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

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

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

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

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

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

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

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:

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

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

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

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

Re: [time-nuts] how to find low noise transistors

: 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

Re: [time-nuts] how to find low noise transistors

- 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

Re: [time-nuts] how to find low noise transistors

On 20 Jul 2015 00:09, Mike Feher mfe...@eozinc.com 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

Re: [time-nuts] how to find low noise transistors

] 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

Re: [time-nuts] how to find low noise transistors

...@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

Re: [time-nuts] how to find low noise transistors

-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

Re: [time-nuts] how to find low noise transistors

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

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?

Re: [time-nuts] how to find low noise transistors

-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

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

Re: [time-nuts] how to find low noise transistors

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

Re: [time-nuts] how to find low noise transistors

...@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

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 csteinm...@yandex.com wrote: A pair of Zetex (Diodes, Inc.) ZTX849 or FZT849 actually have significantly

[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 csteinm...@yandex.com 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

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

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

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

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

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

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

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

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.