Re: [time-nuts] how to find low noise transistors
Good questions , I am looking forward to the answers, this is my area of work ... Ulrich N1UL In a message dated 7/28/2015 1:45:55 P.M. Eastern Daylight Time, dk...@arcor.de writes: Am 20.07.2015 um 01:57 schrieb KA2WEU--- via time-nuts: > Good evening, this turns out to be a good discussion... > > Any more inputs ? 73 de Ulrich > > 1. To get a gut feeling about the virtues of nonlinear noise simulation: how much phase noise will we typically lose if we stay with linear simulation? I mean, we have been told so often how important it is that the amplifier offers a constant (low) impedance to the crystal and that the smallest nonlinearity would be an invitation to noise up conversion. It does not take a lot of conversion gain when one looks at -150 dBc. So, even if we use a HB simulator, the DUT will have to be pretty linear. 2. What do you consider the optimum AGC for, say, a Driscoll or Butler at 100 MHz? In my current work, most of the logic is triple module redundant and the oscillator is a single point of failure. Stopping oscillation at an EFC extreme would be a nightmare, but phase noise performance still cannot be ignored. 3. Is there any work on AGC vs. post tuning drift? 4. In [1] there are is some treatment about removing 1/f noise of a RF transistor by active LF feedback. It is applied to a BFR93A and the effect can be seen clearly. There are other faster transistors that would need that much more urgently, and for > 40 dB of 1/f noise probably more loop gain would be required. I can see a place for an ADA4898 here… Also, there are 1K resistors in the bases of both the RF and the AF transistors while we are discussing here replicating the transistors to shrink the effective base spreading resistance. It seems that the improvement could be much larger. BTW I got -145dBc @100MHz @100Hz with mass production BFR93 transistors in Butlers, and the limit seemed to be ONLY the crystal; most crystals were much worse, even when they had comparable parameters and were from the same batch. 5. One must always find a balance between optimum close-in or far-out noise. The emitter input impedance of a 2 stage Butler sustaining amplifier may serve as an example. Make it small and there will be only a slight operating Q degradation - but less power available to the input of the sustaining amp. with a given crystal current; needing more gain and raising the floor. Make it larger, and you get less operating Q and better floor. Only 10% of a crystal batch seem to provide excellent close-in noise, the others being easily 10 dB worse. These others are more or less free (at least already paid for). They still could be used as a post-filter to shrink the noise floor. It would be necessary to de-Q them with resistors so that they can withstand the power and that they do not spoil the close-in noise. Or use a bridge xtal filter that has no crystal resonance on the center frequency. That would require some discipline when tuning the oscillator to avoid blowing the filter crystals. Far out the noise still would decrease by 6 dB/oct Fourier-frequency-wise. 20 dB better makes the difference between OK and excellent. [1] Rohde/Newkirk: RF/Microwave Circuit Design for Wireless Applications, Wiley very short excerpt for a few days on < https://picasaweb.google.com/lh/photo/XUfeAuD8TvNqBOMuJiPtltMTjNZETYmyPJy0li ipFm0?feat=directlink> 73, Gerhard, DK4XP ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Am 20.07.2015 um 01:57 schrieb KA2WEU--- via time-nuts: Good evening, this turns out to be a good discussion... Any more inputs ? 73 de Ulrich 1. To get a gut feeling about the virtues of nonlinear noise simulation: how much phase noise will we typically lose if we stay with linear simulation? I mean, we have been told so often how important it is that the amplifier offers a constant (low) impedance to the crystal and that the smallest nonlinearity would be an invitation to noise up conversion. It does not take a lot of conversion gain when one looks at -150 dBc. So, even if we use a HB simulator, the DUT will have to be pretty linear. 2. What do you consider the optimum AGC for, say, a Driscoll or Butler at 100 MHz? In my current work, most of the logic is triple module redundant and the oscillator is a single point of failure. Stopping oscillation at an EFC extreme would be a nightmare, but phase noise performance still cannot be ignored. 3. Is there any work on AGC vs. post tuning drift? 4. In [1] there are is some treatment about removing 1/f noise of a RF transistor by active LF feedback. It is applied to a BFR93A and the effect can be seen clearly. There are other faster transistors that would need that much more urgently, and for > 40 dB of 1/f noise probably more loop gain would be required. I can see a place for an ADA4898 here… Also, there are 1K resistors in the bases of both the RF and the AF transistors while we are discussing here replicating the transistors to shrink the effective base spreading resistance. It seems that the improvement could be much larger. BTW I got -145dBc @100MHz @100Hz with mass production BFR93 transistors in Butlers, and the limit seemed to be ONLY the crystal; most crystals were much worse, even when they had comparable parameters and were from the same batch. 5. One must always find a balance between optimum close-in or far-out noise. The emitter input impedance of a 2 stage Butler sustaining amplifier may serve as an example. Make it small and there will be only a slight operating Q degradation - but less power available to the input of the sustaining amp. with a given crystal current; needing more gain and raising the floor. Make it larger, and you get less operating Q and better floor. Only 10% of a crystal batch seem to provide excellent close-in noise, the others being easily 10 dB worse. These others are more or less free (at least already paid for). They still could be used as a post-filter to shrink the noise floor. It would be necessary to de-Q them with resistors so that they can withstand the power and that they do not spoil the close-in noise. Or use a bridge xtal filter that has no crystal resonance on the center frequency. That would require some discipline when tuning the oscillator to avoid blowing the filter crystals. Far out the noise still would decrease by 6 dB/oct Fourier-frequency-wise. 20 dB better makes the difference between OK and excellent. [1] Rohde/Newkirk: RF/Microwave Circuit Design for Wireless Applications, Wiley very short excerpt for a few days on < https://picasaweb.google.com/lh/photo/XUfeAuD8TvNqBOMuJiPtltMTjNZETYmyPJy0liipFm0?feat=directlink> 73, Gerhard, DK4XP ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Rick wrote: OTOH, the other cure for high base spreading resistance is to simply parallel multiple devices. This avoids the bad side effects you mention. Yes, if you can operate each of the transistors at the same current you would have used for a solo transistor. Typically, though, you need to reduce the current through each transistor so that the total current remains approximately the same as you would use for one transistor, in which case you do not escape the side effects. There is a practical limit to increased total current in circuits that use collector resistors to transforn the devices' transconductance into voltage gain -- as you increase the device current, you need to reduce the collector resistors (and, therefore, stage gain) or increase the power supply voltage (which gets out of hand in a hurry). In some cases, this can be avoided by using current source or current mirror collector loads. Also, when paralleling transistors, you need to allow for the noise of any emitter ballasting resistors that may be necessary to equalize currents between the transistors. All is not lost, however -- the parallel device strategy encourages the designer to use multiple, lower current devices to replace a single, higher current device (for example, using multiple 2N5179s to replace a single 2N5109). Some '80s hi-fi preamps went to absurd lengths with parallel input devices. A few had 20 or so devices in parallel for each of the four input devices of a complementary differential pair (x2 for stereo, so 160 input transistors for just one stereo stage). But in order for the input bias and offset currents to remain somewhat reasonable, and for other practical reasons, the current per device had to be reduced to the point that the bad side effects were glaringly apparent. (One more all-too-common example of a designer being blindly committed to his or her Good Idea and pursuing it to the detriment of the product.) Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Brooke wrote:
Does hFE (DC) have much relevance to this? Would hfe (AC) be the
important one?
It depends on whether you are more interested in the 1/f noise, which
causes most of the phase noise in oscillators and the additive
("residual") PN in amplifiers, or the in-band noise. As I said in
the message to which you replied:
Note that these are static (DC) curves, which are good
approximations for the 1/f region. The curves in the white noise
region, even at relatively low frequencies like 1 kHz, generally
fall off faster than this as current is reduced, so the effect of
reduced beta on in-band noise figure is greater.
Best regards,
Charles
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Re: [time-nuts] how to find low noise transistors
On 7/24/2015 11:58 AM, Brooke Clarke wrote: Hi Charles: Does hFE (DC) have much relevance to this? Would hfe (AC) be the important one? Only insofar as DC current gain is an upper bound on AC current gain. If your operating frequency is less than f-sub-t divided by beta, then DC current gain = AC current gain. Rick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Hi Charles: Does hFE (DC) have much relevance to this? Would hfe (AC) be the important one? Mail_Attachment -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Charles Steinmetz wrote: Rick wrote: optimum noise figure is a function of the ratio between base spreading resistance and (beta)(r-sub-e). If base spreading resistance is high, you make r-sub-e high by reducing collector current. I replied: reducing transistor current to raise the noise resistance causes undesirable collateral effects (including reduced bandwidth, which increases phase noise due to baseband noise modulation of transistor capacitances and generally increases nonlinearity). I should also have mentioned: Reducing transistor current also frequently reduces beta (sometimes by a large factor, depending on the transistor's beta vs. current curve and where you are on it). This directly affects (beta)(r-sub-e) and, therefore, directly reduces the noise figure. I've pasted in the beta vs. collector current graphs for the ubiquitous 2N3904 and 2N4401 to illustrate this. Some transistors are better than these over a useful range of collector currents, others are much worse. The beta of PNPs, which are generally quieter than NPNs, also generally falls off faster with reduced collector current. Note that these are static (DC) curves, which are good approximations for the 1/f region. The curves in the white noise region, even at relatively low frequencies like 1 kHz, generally fall off faster than this as current is reduced, so the effect of reduced beta on in-band noise figure is greater. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
OTOH, the other cure for high base spreading resistance is to simply parallel multiple devices. This avoids the bad side effects you mention. The other key noise parameter in a BJT is RF current gain, and this cannot be "cured" by any circuit design tricks. Rick Karlquist N6RK On 7/23/2015 8:29 PM, Charles Steinmetz wrote: Rick wrote: optimum noise figure is a function of the ratio between base spreading resistance and (beta)(r-sub-e). If base spreading resistance is high, you make r-sub-e high by reducing collector current. I replied: reducing transistor current to raise the noise resistance causes undesirable collateral effects (including reduced bandwidth, which increases phase noise due to baseband noise modulation of transistor capacitances and generally increases nonlinearity). I should also have mentioned: Reducing transistor current also frequently reduces beta (sometimes by a large factor, depending on the transistor's beta vs. current curve and where you are on it). This directly affects (beta)(r-sub-e) and, therefore, directly reduces the noise figure. I've pasted in the beta vs. collector current graphs for the ubiquitous 2N3904 and 2N4401 to illustrate this. Some transistors are better than these over a useful range of collector currents, others are much worse. The beta of PNPs, which are generally quieter than NPNs, also generally falls off faster with reduced collector current. Note that these are static (DC) curves, which are good approximations for the 1/f region. The curves in the white noise region, even at relatively low frequencies like 1 kHz, generally fall off faster than this as current is reduced, so the effect of reduced beta on in-band noise figure is greater. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Rick wrote: optimum noise figure is a function of the ratio between base spreading resistance and (beta)(r-sub-e). If base spreading resistance is high, you make r-sub-e high by reducing collector current. I replied: reducing transistor current to raise the noise resistance causes undesirable collateral effects (including reduced bandwidth, which increases phase noise due to baseband noise modulation of transistor capacitances and generally increases nonlinearity). I should also have mentioned: Reducing transistor current also frequently reduces beta (sometimes by a large factor, depending on the transistor's beta vs. current curve and where you are on it). This directly affects (beta)(r-sub-e) and, therefore, directly reduces the noise figure. I've pasted in the beta vs. collector current graphs for the ubiquitous 2N3904 and 2N4401 to illustrate this. Some transistors are better than these over a useful range of collector currents, others are much worse. The beta of PNPs, which are generally quieter than NPNs, also generally falls off faster with reduced collector current. Note that these are static (DC) curves, which are good approximations for the 1/f region. The curves in the white noise region, even at relatively low frequencies like 1 kHz, generally fall off faster than this as current is reduced, so the effect of reduced beta on in-band noise figure is greater. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Rick wrote: When you raise the source impedance, you also have to reduce the collector current. Your analysis didn't take that into account. Refer to page 83 of the first edition of "Low Noise Electronic Design". Equation e. states that optimum noise figure is a function of the ratio between base spreading resistance and (beta)(r-sub-e). If base spreading resistance is high, you make r-sub-e high by reducing collector current. Equation f. states that doing that will increase optimum source resistance. Agreed, you can adjust the "noise resistance" of a BJT (the ratio of its voltage noise to its current noise). However, minimum noise figure is frequently not the way to obtain the least added noise voltage from an amplifier. That is the fallacy I mentioned -- the mistaken notion that increasing the resistance of the source to achieve a better NF will improve the S/N ratio of the amplifier output. That will be true only if (i) one can arbitrarily vary the intrinsic resistance of the source without changing the source's intrinsic S/N ratio, and (ii) one is stuck with a certain BJT input device. Neither is almost ever the case in real life (aside from increasing the source impedance with a transformer). Furthermore, reducing transistor current to raise the noise resistance causes undesirable collateral effects (including reduced bandwidth, which increases phase noise due to baseband noise modulation of transistor capacitances and generally increases nonlinearity). BJTs are readily available with noise resistances of less than 50 ohms (see The Art of Electronics, 3rd edition, Chapter 8). The only reason to increase the source impedance with a transformer is if the intrinsic source impedance is lower than the lowest available BJT noise resistance -- for example, in the case of microwave transistors (remember, this thread started in reference to LN preamps for 100kHz LORAN antennas). Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
73 de Ulrich, N1UL Update on crysral oscillators Techniques minimize the phase noise in crystal oscillator circuits Poddar, A.K. ; Rohde, U.L. Frequency Control Symposium (FCS), 2012 IEEE International DOI: 10.1109/FCS.2012.6243701 Publication Year: 2012 , Page(s): 1 - 7 Cited by: Papers (1) IEEE CONFERENCE PUBLICATIONS Full text access may be available. Click article title to sign in or learn about subscription options.How Low Can They Go?: Oscillator Phase Noise Model, Theoretical, Experimental Validation, and Phase Noise Measurements Poddar, A.K. ; Rohde, U.L. ; Apte, A.M. Microwave Magazine, IEEE Volume: 14 , Issue: 6 DOI: 10.1109/MMM.2013.2269859 Publication Year: 2013 , Page(s): 50 - 72 Cited by: Papers (4) IEEE JOURNALS & MAGAZINES Getting Its Measure: Oscillator Phase Noise Measurement Techniques and Limitations Rohde, U.L. ; Poddar, A.K. ; Apte, A.M. Microwave Magazine, IEEE Volume: 14 , Issue: 6 DOI: 10.1109/MMM.2013.2269860 Publication Year: 2013 , Page(s): 73 - 86 Cited by: Papers (5) _Reply With Quote_ (http://www.edaboard.com/newreply.php?do=newreply&p=1442491) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
On 7/20/2015 8:12 AM, Charles Steinmetz wrote: Rick wrote: Base spreading resistance can be overcome by using a sufficiently high source impedance This sounds like the all-too-common noise figure fallacy (increasing input impedance to get a lower NF). All this does is raise the source impedance's contribution to the total noise -- it doesn't reduce the amplifier input noise voltage, and it increases the amplifier noise due to input noise current. The result is more output noise, not less, and a reduced signal to noise ratio, despite the improved NF. Even if you use a transformer to raise the source impedance, the signal voltage increases by the turns ratio while the impedance increases by the square of the turns ratio (thus, the output noise due to the amplifier input noise current flowing through the source impedance also increases as the square of the turns ratio). Best regards, Charles When you raise the source impedance, you also have to reduce the collector current. Your analysis didn't take that into account. Refer to page 83 of the first edition of "Low Noise Electronic Design". Equation e. states that optimum noise figure is a function of the ratio between base spreading resistance and (beta)(r-sub-e). If base spreading resistance is high, you make r-sub-e high by reducing collector current. Equation f. states that doing that will increase optimum source resistance. Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Rick wrote: Base spreading resistance can be overcome by using a sufficiently high source impedance This sounds like the all-too-common noise figure fallacy (increasing input impedance to get a lower NF). All this does is raise the source impedance's contribution to the total noise -- it doesn't reduce the amplifier input noise voltage, and it increases the amplifier noise due to input noise current. The result is more output noise, not less, and a reduced signal to noise ratio, despite the improved NF. Even if you use a transformer to raise the source impedance, the signal voltage increases by the turns ratio while the impedance increases by the square of the turns ratio (thus, the output noise due to the amplifier input noise current flowing through the source impedance also increases as the square of the turns ratio). Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Also a good paper: Phase Noise Reduction in Microwave Oscillators Alexander Chenakin, Phase Matrix Inc., San Jose, CA <http://www.microwavejournal.com/authors/1981-alexander-chenakin-phase-matrix-inc-san-jose-ca> http://www.microwavejournal.com/articles/8625-phase-noise-reduction-in-microwave-oscillators?v=preview 73 Alex On 7/19/2015 8:00 AM, Azelio Boriani wrote: Yes, I'm with Bob Pease: the soldering iron is my best simulation tool. Nonetheless it is useful to know how to correctly extract the coefficients to use in the best known among the simulation tools. In one sci.electronics.design discussion, A. Lakovlev tells to have determined the KF based on the datasheet's NF by trials and then adjusted AF to follow the datasheet's NF variation with the collector current. He ended up with KF= 5E-15 and AF= 1.13 for the 2SC3329, also in this case the AF is greater than 1. On Sun, Jul 19, 2015 at 4:41 PM, wrote: For HF to uW oscillators if find these modeling efforts not adequate . Only a test circuit will show the prove... Ulrich N1UL In a message dated 7/19/2015 10:36:10 A.M. Eastern Daylight Time, azelio.bori...@gmail.com writes: For a method to extract AF and KF try this: <http://joerg-berkner.de/Fachartikel/pdf/2000_AKB_Berkner_1f_noise.pdf> see also <http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=2270&context=etd> from page 55, on the parameter extraction for the BJTs usually AF is greater than 1, as you can see in this appnote from CEL: <http://www.cel.com/pdf/appnotes/an1026.pdf> A SILVACO appnote on how to model for SPICE2 for 1/f (from page 45): <http://www.silvaco.com/content/kbase/noise_modeling.pdf> On Sun, Jul 19, 2015 at 4:59 AM, John Miles wrote: -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of KA2WEU-- - via time-nuts Sent: Saturday, July 18, 2015 3:40 PM To: time-nuts@febo.com Cc: akpod...@synergymwave.com; alexander.r...@rohde-schwarz.com Subject: Re: [time-nuts] how to find low noise transistors BFG540 That's what I mean -- both BFG540 and BFG591 have been discontinued by NXP. Guess they don't sell enough of them these days. -- john, KE5FX Miles Design LLC ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Good evening, this turns out to be a good discussion... Any more inputs ? 73 de Ulrich In a message dated 7/19/2015 7:13:39 P.M. Eastern Daylight Time, rich...@karlquist.com writes: On 7/18/2015 2:16 AM, Attila Kinali wrote: > > I always wonder how you figure out whether a transistor is low noise > or not. What part of the datasheet hints at which transistors have low > noise and which have not? Even if it's just try and measure, how > do you find good candidates to measure? > >Attila Kinali > For a BJT operating above the 1/f noise corner, and at non-microwave frequencies, the noise properties depend only on RF current gain and base spreading resistance. See "Low noise electronic design" by Motchenbacher and Fitchen. RF (not DC) current gain can be measured the usual ways, but base spreading resistance has to be inferred from noise figure measurements made with low source resistance. The RF current gain is the real fundamental noise property of the device that you cannot change. Fortunately, it can be determined from the data sheet, if not directly, then by calculating it from DC current gain and F-sub-t, based on the operating frequency. The low frequency current noise (above the 1/f corner) is simply equal to the shot noise of the DC base current. The low frequency voltage noise is the sum of the Johnson noise that a resistor would have if its value were the sum of the base spreading resistance and half of r-sub-e. Where r-sub-e is the "emitter resistance",IE the effective on resistance of the transistor. Base spreading resistance can be overcome by using a sufficiently high source impedance and/or paralleling devices (if you can tolerate the additional capacitance). At frequencies such as 100 kHz and 10 MHz, it is very easy to get a noise figure well below 1 dB with a BJT, so it should be no great problem to find a suitable device. Even lower noise figures are available with JFET's, which have noise current equal to the shot noise of gate current, which is specified. The resulting noise current is negligible for most devices. This leaves the noise voltage, which is just the Johnson noise of a resistor equal to the channel resistance. By scaling to larger devices and/or paralleling devices, this can be reduced to arbitrarily low values. The limiting factor is the substantial capacitance of JFET's. This limits them to about 1 to 10 MHz, before high beta BJT's dominate. I have observed noise figure of below 0.2 dB in JFET's at 2 MHz. Below 50 to 100 MHz, MOSFET's and ePHEMT's have excessive 1/f noise and are a non starter. Above the 1/f corner, it is easy to get noise figures of a few tenths of a dB with ePHEMT's. All of this discussion doesn't address 1/f noise, which could be an issue in oscillators and low phase noise amplifiers. For that purpose, you are back to characterizing devices yourself. Putting negative feedback around the transistor can alleviate this by reducing upconversion of noise. Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
some old but very good papers: Roger Muat, “Choosing devices for quiet oscillators”, Microwave & RF, August 1984, pp. 166-170. Grant Moulton, “Dig for the roots of oscillator noise”, Microwave & RF, pp. 65-69, April 1986. Julio Costa et al, “Extracting 1/f Noise Coefficients for BJT’s,” IEEE Transactions on Electron Devices, Vol. 41, No.11, pp. 1992-1999, Nov. 1994 “Simulating Noise in Nonlinear Circuits Using the HP Microwave and RF Design Systems,” HP Product note 85180- 4, c 1993. 73 Alex On 7/19/2015 8:00 AM, Azelio Boriani wrote: Yes, I'm with Bob Pease: the soldering iron is my best simulation tool. Nonetheless it is useful to know how to correctly extract the coefficients to use in the best known among the simulation tools. In one sci.electronics.design discussion, A. Lakovlev tells to have determined the KF based on the datasheet's NF by trials and then adjusted AF to follow the datasheet's NF variation with the collector current. He ended up with KF= 5E-15 and AF= 1.13 for the 2SC3329, also in this case the AF is greater than 1. On Sun, Jul 19, 2015 at 4:41 PM, wrote: For HF to uW oscillators if find these modeling efforts not adequate . Only a test circuit will show the prove... Ulrich N1UL In a message dated 7/19/2015 10:36:10 A.M. Eastern Daylight Time, azelio.bori...@gmail.com writes: For a method to extract AF and KF try this: <http://joerg-berkner.de/Fachartikel/pdf/2000_AKB_Berkner_1f_noise.pdf> see also <http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=2270&context=etd> from page 55, on the parameter extraction for the BJTs usually AF is greater than 1, as you can see in this appnote from CEL: <http://www.cel.com/pdf/appnotes/an1026.pdf> A SILVACO appnote on how to model for SPICE2 for 1/f (from page 45): <http://www.silvaco.com/content/kbase/noise_modeling.pdf> On Sun, Jul 19, 2015 at 4:59 AM, John Miles wrote: -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of KA2WEU-- - via time-nuts Sent: Saturday, July 18, 2015 3:40 PM To: time-nuts@febo.com Cc: akpod...@synergymwave.com; alexander.r...@rohde-schwarz.com Subject: Re: [time-nuts] how to find low noise transistors BFG540 That's what I mean -- both BFG540 and BFG591 have been discontinued by NXP. Guess they don't sell enough of them these days. -- john, KE5FX Miles Design LLC ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
I simply do not belief 5E-15 . Ulrich In a message dated 7/19/2015 7:12:05 P.M. Eastern Daylight Time, azelio.bori...@gmail.com writes: Yes, I'm with Bob Pease: the soldering iron is my best simulation tool. Nonetheless it is useful to know how to correctly extract the coefficients to use in the best known among the simulation tools. In one sci.electronics.design discussion, A. Lakovlev tells to have determined the KF based on the datasheet's NF by trials and then adjusted AF to follow the datasheet's NF variation with the collector current. He ended up with KF= 5E-15 and AF= 1.13 for the 2SC3329, also in this case the AF is greater than 1. On Sun, Jul 19, 2015 at 4:41 PM, wrote: > For HF to uW oscillators if find these modeling efforts not adequate . Only > a test circuit will show the prove... > > Ulrich N1UL > > In a message dated 7/19/2015 10:36:10 A.M. Eastern Daylight Time, > azelio.bori...@gmail.com writes: > > For a method to extract AF and KF try this: > <http://joerg-berkner.de/Fachartikel/pdf/2000_AKB_Berkner_1f_noise.pdf> > > see also > <http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=2270&cont ext=etd> > from page 55, on the parameter extraction for the BJTs > > usually AF is greater than 1, as you can see in this appnote from CEL: > <http://www.cel.com/pdf/appnotes/an1026.pdf> > > A SILVACO appnote on how to model for SPICE2 for 1/f (from page 45): > <http://www.silvaco.com/content/kbase/noise_modeling.pdf> > > On Sun, Jul 19, 2015 at 4:59 AM, John Miles wrote: >> >>> -Original Message- >>> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of KA2WEU-- >>> - via time-nuts >>> Sent: Saturday, July 18, 2015 3:40 PM >>> To: time-nuts@febo.com >>> Cc: akpod...@synergymwave.com; alexander.r...@rohde-schwarz.com >>> Subject: Re: [time-nuts] how to find low noise transistors >>> >>> BFG540 >>> >>> >> >> That's what I mean -- both BFG540 and BFG591 have been discontinued by >> NXP. Guess they don't sell enough of them these days. >> >> -- john, KE5FX >> Miles Design LLC >> >> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
On 20 Jul 2015 00:09, "Mike Feher" wrote: > > But they can be found very inexpensively on eBay. 73 - Mike There are a lot of fake transistors on eBay. There was a report on the HP/Agilent list where someone bought 10 IC's from eBay as a test. Not one was genuine. Personally I would not buy semiconductors from eBay. The probability of getting fake devices appears to be fairly high. Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Hate to be an echo but be very careful. What you can get on EBay is things like rejects, rebranded junk, used pulls. Reports have been published where even parts that sell for 10 cents were profitable enough to rebrand parts. A case of say 10th spoils of 5,000 each transistors can be had for less then $5 and it cost about 2 cents to remark them. On Jul 19, 2015 4:08 PM, "Mike Feher" wrote: > But they can be found very inexpensively on eBay. 73 - Mike > > Mike B. Feher, EOZ Inc. > 89 Arnold Blvd. > Howell, NJ, 07731 > 732-886-5960 office > 908-902-3831 cell > > > -Original Message- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of John > Miles > Sent: Saturday, July 18, 2015 11:00 PM > To: 'Discussion of precise time and frequency measurement' > Subject: Re: [time-nuts] how to find low noise transistors > > > > -Original Message- > > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of > > KA2WEU-- > > - via time-nuts > > Sent: Saturday, July 18, 2015 3:40 PM > > To: time-nuts@febo.com > > Cc: akpod...@synergymwave.com; alexander.r...@rohde-schwarz.com > > Subject: Re: [time-nuts] how to find low noise transistors > > > > BFG540 > > > > > > That's what I mean -- both BFG540 and BFG591 have been discontinued by > NXP. Guess they don't sell enough of them these days. > > -- john, KE5FX > Miles Design LLC > > > ___ > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
The first reference is audio only, no RF component, Ref 2 is questionable as the SSB analyzer lacks the low frequency dynamic range, at 1 Hz and below it should be more like 40dB/Hz , a 100 MHz crystal oscillator as a test would have ben better . But he is much more hones using AF=2, maybe slightly off, but not 1 as some use. About CEL : FOR SSB noise not useful but at least it shows that AF and KF , both, are bias dependent, must forget this . SILVACO page 112 again is low frequency modeling, not applicable for RF, one need to know the AM/PM conversion. This is a real tough subject and most approaches are incorrectly, use curve fitting or test equipment with not enough dynamic range ... 73 de Ulrich , N1UL In a message dated 7/19/2015 10:36:10 A.M. Eastern Daylight Time, azelio.bori...@gmail.com writes: For a method to extract AF and KF try this: <http://joerg-berkner.de/Fachartikel/pdf/2000_AKB_Berkner_1f_noise.pdf> see also <http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=2270&context=etd> from page 55, on the parameter extraction for the BJTs usually AF is greater than 1, as you can see in this appnote from CEL: <http://www.cel.com/pdf/appnotes/an1026.pdf> A SILVACO appnote on how to model for SPICE2 for 1/f (from page 45): <http://www.silvaco.com/content/kbase/noise_modeling.pdf> On Sun, Jul 19, 2015 at 4:59 AM, John Miles wrote: > >> -Original Message- >> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of KA2WEU-- >> - via time-nuts >> Sent: Saturday, July 18, 2015 3:40 PM >> To: time-nuts@febo.com >> Cc: akpod...@synergymwave.com; alexander.r...@rohde-schwarz.com >> Subject: Re: [time-nuts] how to find low noise transistors >> >> BFG540 >> >> > > That's what I mean -- both BFG540 and BFG591 have been discontinued by NXP. Guess they don't sell enough of them these days. > > -- john, KE5FX > Miles Design LLC > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
On 7/18/2015 2:16 AM, Attila Kinali wrote: I always wonder how you figure out whether a transistor is low noise or not. What part of the datasheet hints at which transistors have low noise and which have not? Even if it's just try and measure, how do you find good candidates to measure? Attila Kinali For a BJT operating above the 1/f noise corner, and at non-microwave frequencies, the noise properties depend only on RF current gain and base spreading resistance. See "Low noise electronic design" by Motchenbacher and Fitchen. RF (not DC) current gain can be measured the usual ways, but base spreading resistance has to be inferred from noise figure measurements made with low source resistance. The RF current gain is the real fundamental noise property of the device that you cannot change. Fortunately, it can be determined from the data sheet, if not directly, then by calculating it from DC current gain and F-sub-t, based on the operating frequency. The low frequency current noise (above the 1/f corner) is simply equal to the shot noise of the DC base current. The low frequency voltage noise is the sum of the Johnson noise that a resistor would have if its value were the sum of the base spreading resistance and half of r-sub-e. Where r-sub-e is the "emitter resistance",IE the effective on resistance of the transistor. Base spreading resistance can be overcome by using a sufficiently high source impedance and/or paralleling devices (if you can tolerate the additional capacitance). At frequencies such as 100 kHz and 10 MHz, it is very easy to get a noise figure well below 1 dB with a BJT, so it should be no great problem to find a suitable device. Even lower noise figures are available with JFET's, which have noise current equal to the shot noise of gate current, which is specified. The resulting noise current is negligible for most devices. This leaves the noise voltage, which is just the Johnson noise of a resistor equal to the channel resistance. By scaling to larger devices and/or paralleling devices, this can be reduced to arbitrarily low values. The limiting factor is the substantial capacitance of JFET's. This limits them to about 1 to 10 MHz, before high beta BJT's dominate. I have observed noise figure of below 0.2 dB in JFET's at 2 MHz. Below 50 to 100 MHz, MOSFET's and ePHEMT's have excessive 1/f noise and are a non starter. Above the 1/f corner, it is easy to get noise figures of a few tenths of a dB with ePHEMT's. All of this discussion doesn't address 1/f noise, which could be an issue in oscillators and low phase noise amplifiers. For that purpose, you are back to characterizing devices yourself. Putting negative feedback around the transistor can alleviate this by reducing upconversion of noise. Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Yes, I'm with Bob Pease: the soldering iron is my best simulation tool. Nonetheless it is useful to know how to correctly extract the coefficients to use in the best known among the simulation tools. In one sci.electronics.design discussion, A. Lakovlev tells to have determined the KF based on the datasheet's NF by trials and then adjusted AF to follow the datasheet's NF variation with the collector current. He ended up with KF= 5E-15 and AF= 1.13 for the 2SC3329, also in this case the AF is greater than 1. On Sun, Jul 19, 2015 at 4:41 PM, wrote: > For HF to uW oscillators if find these modeling efforts not adequate . Only > a test circuit will show the prove... > > Ulrich N1UL > > In a message dated 7/19/2015 10:36:10 A.M. Eastern Daylight Time, > azelio.bori...@gmail.com writes: > > For a method to extract AF and KF try this: > <http://joerg-berkner.de/Fachartikel/pdf/2000_AKB_Berkner_1f_noise.pdf> > > see also > <http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=2270&context=etd> > from page 55, on the parameter extraction for the BJTs > > usually AF is greater than 1, as you can see in this appnote from CEL: > <http://www.cel.com/pdf/appnotes/an1026.pdf> > > A SILVACO appnote on how to model for SPICE2 for 1/f (from page 45): > <http://www.silvaco.com/content/kbase/noise_modeling.pdf> > > On Sun, Jul 19, 2015 at 4:59 AM, John Miles wrote: >> >>> -Original Message- >>> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of KA2WEU-- >>> - via time-nuts >>> Sent: Saturday, July 18, 2015 3:40 PM >>> To: time-nuts@febo.com >>> Cc: akpod...@synergymwave.com; alexander.r...@rohde-schwarz.com >>> Subject: Re: [time-nuts] how to find low noise transistors >>> >>> BFG540 >>> >>> >> >> That's what I mean -- both BFG540 and BFG591 have been discontinued by >> NXP. Guess they don't sell enough of them these days. >> >> -- john, KE5FX >> Miles Design LLC >> >> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
For HF to uW oscillators if find these modeling efforts not adequate . Only a test circuit will show the prove... Ulrich N1UL In a message dated 7/19/2015 10:36:10 A.M. Eastern Daylight Time, azelio.bori...@gmail.com writes: For a method to extract AF and KF try this: <http://joerg-berkner.de/Fachartikel/pdf/2000_AKB_Berkner_1f_noise.pdf> see also <http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=2270&context=etd> from page 55, on the parameter extraction for the BJTs usually AF is greater than 1, as you can see in this appnote from CEL: <http://www.cel.com/pdf/appnotes/an1026.pdf> A SILVACO appnote on how to model for SPICE2 for 1/f (from page 45): <http://www.silvaco.com/content/kbase/noise_modeling.pdf> On Sun, Jul 19, 2015 at 4:59 AM, John Miles wrote: > >> -Original Message- >> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of KA2WEU-- >> - via time-nuts >> Sent: Saturday, July 18, 2015 3:40 PM >> To: time-nuts@febo.com >> Cc: akpod...@synergymwave.com; alexander.r...@rohde-schwarz.com >> Subject: Re: [time-nuts] how to find low noise transistors >> >> BFG540 >> >> > > That's what I mean -- both BFG540 and BFG591 have been discontinued by NXP. Guess they don't sell enough of them these days. > > -- john, KE5FX > Miles Design LLC > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
But they can be found very inexpensively on eBay. 73 - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of John Miles Sent: Saturday, July 18, 2015 11:00 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] how to find low noise transistors > -Original Message- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of > KA2WEU-- > - via time-nuts > Sent: Saturday, July 18, 2015 3:40 PM > To: time-nuts@febo.com > Cc: akpod...@synergymwave.com; alexander.r...@rohde-schwarz.com > Subject: Re: [time-nuts] how to find low noise transistors > > BFG540 > > That's what I mean -- both BFG540 and BFG591 have been discontinued by NXP. Guess they don't sell enough of them these days. -- john, KE5FX Miles Design LLC ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
For a method to extract AF and KF try this: <http://joerg-berkner.de/Fachartikel/pdf/2000_AKB_Berkner_1f_noise.pdf> see also <http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=2270&context=etd> from page 55, on the parameter extraction for the BJTs usually AF is greater than 1, as you can see in this appnote from CEL: <http://www.cel.com/pdf/appnotes/an1026.pdf> A SILVACO appnote on how to model for SPICE2 for 1/f (from page 45): <http://www.silvaco.com/content/kbase/noise_modeling.pdf> On Sun, Jul 19, 2015 at 4:59 AM, John Miles wrote: > >> -Original Message- >> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of KA2WEU-- >> - via time-nuts >> Sent: Saturday, July 18, 2015 3:40 PM >> To: time-nuts@febo.com >> Cc: akpod...@synergymwave.com; alexander.r...@rohde-schwarz.com >> Subject: Re: [time-nuts] how to find low noise transistors >> >> BFG540 >> >> > > That's what I mean -- both BFG540 and BFG591 have been discontinued by NXP. > Guess they don't sell enough of them these days. > > -- john, KE5FX > Miles Design LLC > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
> -Original Message- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of KA2WEU-- > - via time-nuts > Sent: Saturday, July 18, 2015 3:40 PM > To: time-nuts@febo.com > Cc: akpod...@synergymwave.com; alexander.r...@rohde-schwarz.com > Subject: Re: [time-nuts] how to find low noise transistors > > BFG540 > > That's what I mean -- both BFG540 and BFG591 have been discontinued by NXP. Guess they don't sell enough of them these days. -- john, KE5FX Miles Design LLC ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
BFG540 In a message dated 7/18/2015 6:37:34 P.M. Eastern Daylight Time, j...@miles.io writes: Last time buy 31-Dec-15. :( Have you heard of any good substitutes? I've built a lot of amps with BFG591s, and they also got the axe recently. Small-signal RF bipolars seem to be an endangered species. -- john, KE5FX Miles Design LLC ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Good afternoon, another low noise recommended transistor is the http://www.cel.com/pdf/datasheets/ne856m02.pdf and for frequencies below 10 Mhz the 2N2857. This nice fact is that the AF and KF values are published, the bad part is the the AF=1 value violates the law of physics. http://www.microsemi.com/existing-parts/parts/47966 http://espice.ugr.es/espice/src/modelos_subckt/spice_complete/RF.LIB Be careful ! Who says EE is easy. Best regards , Ulrich N1UL In a message dated 7/18/2015 3:56:53 P.M. Eastern Daylight Time, time-nuts@febo.com writes: Good afternoon, There is a problem in the literature that people confuse the "spot noise figure" and the "large signal " noise properties. Here AF and KF needs to be known and considered. Here is the mathematical correct formula in a Word for Windows Form attached file. If you use it for publications, please quote me . Thanks My advise is take a BIP transistor , fT not much more then 20 x operating frequency (lower flicker component) and operate it at 15 to 20 % of ICmax. The BFG540 is amongst the best Oscillators oscillators http://www.nxp.com/documents/data_sheet/BFG540_X_XR_N.pdf Now you outperform most colleagues 73 de Ulrich N1UL x In a message dated 7/18/2015 1:19:57 P.M. Eastern Daylight Time, p...@petelancashire.com writes: https://scholar.google.com/scholar?q=measuring+transistor+noise&hl=en&as_sdt =0&as_vis=1&oi=scholart ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
> The BFG540 is amongst the best Oscillators oscillators > > http://www.nxp.com/documents/data_sheet/BFG540_X_XR_N.pdf > > Now you outperform most colleagues > > 73 de Ulrich N1UL Last time buy 31-Dec-15. :( Have you heard of any good substitutes? I've built a lot of amps with BFG591s, and they also got the axe recently. Small-signal RF bipolars seem to be an endangered species. -- john, KE5FX Miles Design LLC ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
but be sure that you have a hp4470B --a transistor noise analyzer [ http://www.testequipmenthq.com/datasheets/Agilent-4470B-Datasheet.pdf ] 73 Alex On 7/18/2015 8:47 AM, Pete Lancashire wrote: I agree with Bob, find a vendor you can trust and make sure you buy from an authorized distributor or if just need two or three parts try to get them as samples.directly from the manufacturer. The reason for this is you may get a fake or reject part and you will never know. Trying to do the measurements yourself is pretty much out of the question today.. Every improvement made it harder in that the equipment had to itself be lower in noise If interested https://scholar.google.com/scholar?q=measuring+transistor+noise&hl=en&as_sdt=0&as_vis=1&oi=scholart . -pete On Sat, Jul 18, 2015 at 5:29 AM, Bob Camp wrote: Hi You have (and always have had) two basic choices: 1) Buy a very expensive part from somebody who has gone to the trouble of characterizing the noise performance and will guarantee at least some of what they show on the data sheet. 2) Buy a bunch of cheap transistors and test them. Lock in on a specific part and vendor. Keep monitoring what you get in case they “improve” their process and the magic goes away. How do you select candidates? That’s never been easy, there is less and less data on the sheets every day. Normally the first step is to look at a vendor that you have had luck with in the past. The next step is to ask them… Bob On Jul 18, 2015, at 5:16 AM, Attila Kinali wrote: On Fri, 17 Jul 2015 23:25:10 -0400 Charles Steinmetz wrote: A pair of Zetex (Diodes, Inc.) ZTX849 or FZT849 actually have significantly lower voltage noise than either the LM394 or MAT12. I always wonder how you figure out whether a transistor is low noise or not. What part of the datasheet hints at which transistors have low noise and which have not? Even if it's just try and measure, how do you find good candidates to measure? Attila Kinali -- I must not become metastable. Metastability is the mind-killer. Metastability is the little-death that brings total obliteration. I will face my metastability. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the metastability has gone there will be nothing. Only I will remain. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
Good afternoon, There is a problem in the literature that people confuse the "spot noise figure" and the "large signal " noise properties. Here AF and KF needs to be known and considered. Here is the mathematical correct formula in a Word for Windows Form attached file. If you use it for publications, please quote me . Thanks My advise is take a BIP transistor , fT not much more then 20 x operating frequency (lower flicker component) and operate it at 15 to 20 % of ICmax. The BFG540 is amongst the best Oscillators oscillators http://www.nxp.com/documents/data_sheet/BFG540_X_XR_N.pdf Now you outperform most colleagues 73 de Ulrich N1UL x In a message dated 7/18/2015 1:19:57 P.M. Eastern Daylight Time, p...@petelancashire.com writes: https://scholar.google.com/scholar?q=measuring+transistor+noise&hl=en&as_sdt =0&as_vis=1&oi=scholart OscPN.docx Description: Binary data ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors (was: Firmware and antenna for Stanford Research FS700)
I agree with Bob, find a vendor you can trust and make sure you buy from an authorized distributor or if just need two or three parts try to get them as samples.directly from the manufacturer. The reason for this is you may get a fake or reject part and you will never know. Trying to do the measurements yourself is pretty much out of the question today.. Every improvement made it harder in that the equipment had to itself be lower in noise If interested https://scholar.google.com/scholar?q=measuring+transistor+noise&hl=en&as_sdt=0&as_vis=1&oi=scholart . -pete On Sat, Jul 18, 2015 at 5:29 AM, Bob Camp wrote: > Hi > > You have (and always have had) two basic choices: > > 1) Buy a very expensive part from somebody who has gone to the trouble > of characterizing the noise performance and will guarantee at least some > of what they show on the data sheet. > > 2) Buy a bunch of cheap transistors and test them. Lock in on a > specific part and vendor. Keep monitoring what you get in case they > “improve” > their process and the magic goes away. > > How do you select candidates? That’s never been easy, there is less and > less data on the sheets every day. Normally the first step is to look at > a vendor that you have had luck with in the past. The next step is to ask > them… > > Bob > > > > > On Jul 18, 2015, at 5:16 AM, Attila Kinali wrote: > > > > On Fri, 17 Jul 2015 23:25:10 -0400 > > Charles Steinmetz wrote: > > > >> A pair of Zetex (Diodes, Inc.) > >> ZTX849 or FZT849 actually have significantly lower voltage noise than > >> either the LM394 or MAT12. > > > > I always wonder how you figure out whether a transistor is low noise > > or not. What part of the datasheet hints at which transistors have low > > noise and which have not? Even if it's just try and measure, how > > do you find good candidates to measure? > > > > Attila Kinali > > > > -- > > I must not become metastable. > > Metastability is the mind-killer. > > Metastability is the little-death that brings total obliteration. > > I will face my metastability. > > I will permit it to pass over me and through me. > > And when it has gone past I will turn the inner eye to see its path. > > Where the metastability has gone there will be nothing. Only I will > remain. > > > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors
noise figure, noise voltage, noise current: http://www.ti.com/lit/an/slyt094/slyt094.pdf On 7/18/2015 2:16 AM, Attila Kinali wrote: On Fri, 17 Jul 2015 23:25:10 -0400 Charles Steinmetz wrote: A pair of Zetex (Diodes, Inc.) ZTX849 or FZT849 actually have significantly lower voltage noise than either the LM394 or MAT12. I always wonder how you figure out whether a transistor is low noise or not. What part of the datasheet hints at which transistors have low noise and which have not? Even if it's just try and measure, how do you find good candidates to measure? Attila Kinali ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] how to find low noise transistors (was: Firmware and antenna for Stanford Research FS700)
Hi You have (and always have had) two basic choices: 1) Buy a very expensive part from somebody who has gone to the trouble of characterizing the noise performance and will guarantee at least some of what they show on the data sheet. 2) Buy a bunch of cheap transistors and test them. Lock in on a specific part and vendor. Keep monitoring what you get in case they “improve” their process and the magic goes away. How do you select candidates? That’s never been easy, there is less and less data on the sheets every day. Normally the first step is to look at a vendor that you have had luck with in the past. The next step is to ask them… Bob > On Jul 18, 2015, at 5:16 AM, Attila Kinali wrote: > > On Fri, 17 Jul 2015 23:25:10 -0400 > Charles Steinmetz wrote: > >> A pair of Zetex (Diodes, Inc.) >> ZTX849 or FZT849 actually have significantly lower voltage noise than >> either the LM394 or MAT12. > > I always wonder how you figure out whether a transistor is low noise > or not. What part of the datasheet hints at which transistors have low > noise and which have not? Even if it's just try and measure, how > do you find good candidates to measure? > > Attila Kinali > > -- > I must not become metastable. > Metastability is the mind-killer. > Metastability is the little-death that brings total obliteration. > I will face my metastability. > I will permit it to pass over me and through me. > And when it has gone past I will turn the inner eye to see its path. > Where the metastability has gone there will be nothing. Only I will remain. > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] how to find low noise transistors (was: Firmware and antenna for Stanford Research FS700)
On Fri, 17 Jul 2015 23:25:10 -0400 Charles Steinmetz wrote: > A pair of Zetex (Diodes, Inc.) > ZTX849 or FZT849 actually have significantly lower voltage noise than > either the LM394 or MAT12. I always wonder how you figure out whether a transistor is low noise or not. What part of the datasheet hints at which transistors have low noise and which have not? Even if it's just try and measure, how do you find good candidates to measure? Attila Kinali -- I must not become metastable. Metastability is the mind-killer. Metastability is the little-death that brings total obliteration. I will face my metastability. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the metastability has gone there will be nothing. Only I will remain. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
