Re: [time-nuts] Xtal-like Colpitts Oscillator
Thanks so much for the feedbacks! -Jenny > Date: Tue, 1 Apr 2008 13:18:18 +1300> From: [EMAIL PROTECTED]> To: time-nuts@febo.com> Subject: Re: [time-nuts] Xtal-like Colpitts Oscillator> > Max Robinson wrote:> > Jenny asked.> >> > Hi Everyone, I was hoping to get some words of wisdom on my oscillator that > > only oscillates in simulation! I have a MEMS device that resonates around > > 34 MHz at a given bias with Q of 100.> >> > You have already received some very good advice. You might also try a > > transistor with a higher ft. My personal experience is that it's easier to > > get an FET to oscillate in a colpits configuration. You won't be able to > > drive a 50 ohm load from an FET. A buffer of some kind will definitely be > > needed.> >> > Regards.> >> > Max. K 4 O D S.> >> > > Max> > Lowest noise is achieved when the oscillator transistor only conducts > for part of the cycle.> Altering the ratio of C1 to C2 adjusts the duty cycle.> > With the given values of C1 and C2 a high(~ 30ms) transconductance FET > is required given the relatively high resonator ESR (~200 ohms).> Even when using something like a J310 the values of C1 and C2 will need > to be reduced.> > One option achieving a clean low noise output signal is to extract the > output signal via the resonator.> Instead of grounding one end of the resonator it is connected to the > emitter of a common base stage.> > One could even use the Pound technique to interrogate the MEMs resonance.> In which case, determining the MEMs fundamental resonance frequency to > within a few ppm of fr/Q should be possible.> > Bruce> > ___> 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. _ Test your Star IQ http://club.live.com/red_carpet_reveal.aspx?icid=redcarpet_HMTAGMAR ___ 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] Xtal-like Colpitts Oscillator
Max Robinson wrote: > Jenny asked. > > Hi Everyone, I was hoping to get some words of wisdom on my oscillator that > only oscillates in simulation! I have a MEMS device that resonates around > 34 MHz at a given bias with Q of 100. > > You have already received some very good advice. You might also try a > transistor with a higher ft. My personal experience is that it's easier to > get an FET to oscillate in a colpits configuration. You won't be able to > drive a 50 ohm load from an FET. A buffer of some kind will definitely be > needed. > > Regards. > > Max. K 4 O D S. > > Max Lowest noise is achieved when the oscillator transistor only conducts for part of the cycle. Altering the ratio of C1 to C2 adjusts the duty cycle. With the given values of C1 and C2 a high(~ 30ms) transconductance FET is required given the relatively high resonator ESR (~200 ohms). Even when using something like a J310 the values of C1 and C2 will need to be reduced. One option achieving a clean low noise output signal is to extract the output signal via the resonator. Instead of grounding one end of the resonator it is connected to the emitter of a common base stage. One could even use the Pound technique to interrogate the MEMs resonance. In which case, determining the MEMs fundamental resonance frequency to within a few ppm of fr/Q should be possible. Bruce ___ 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] Xtal-like Colpitts Oscillator
Jenny Lee wrote: > Hi Everyone, I was hoping to get some words of wisdom on my oscillator that > only oscillates in simulation! I have a MEMS device that resonates around 34 > MHz at a given bias with Q of 100. I fit the impedance into a six-element > equivalent model (similar to 4-element equivalent model of Quartz) and placed > in a Colpitts configuration for the simulation. In the open-loop gain/phase > plot, the peak barely passes 0 dB no matter what C1 and C2 I chose. For > transient simulation, it does oscillates, but on a PCB, the circuit won't > oscillate! I'm including the device impedance, circuit schematics and > simulation results as an attachment. I've managed to oscillate 20 MHz device > which has a higher maximum impedance than 34 MHz devices both in simulation > and on a PCB - but for this I followed the guidelines of Colpitts for Quartz > ranging at 10~20MHz. But above 20 MHz, for Quartz, overtones seem to be the > way to go due to the manufacturing so I couldn't find any reference or > circuits that operates Quartz for 30 MHz~50MHz ranges at a fundamental mode. > I can only use fundamental mode for my device... I would really appreciate > if you could share some of your experiences with Colpitts or any suggestions > of what I can try to make it work... Thank you!-Jenny > Jenny The so called overtone oscillators can also be made to oscillate at the fundamental by suitably selecting the mode selection components. The Driscoll oscillators with a relatively low Q tuned collector tank are perhaps easiest to design. Bruce ___ 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] Xtal-like Colpitts Oscillator
Pete wrote: > Jenny, > > In your schematic I'm assuming the uppermost > transistor connection is the emitter. > > Your bias scheme is unlikely to exhibit its "paper" > impedance at 34MHz. Any stray capacitance(s) > can easily result in AC paths to ground lower > than the L & R impedances in your circuit. > > The bias inductor will have a sef-resonant > frequency well below your planned operating > frequency. This inductor is probably useless. > > You need to modify your circuit model by > adding a bunch of stray elements before it > will be apparent why it doesn't work. > > Regards, > Pete Rawson > > If you use a VHF choke similar to those produced by Siemens Matsushita, a 220uH choke has a maximum impedance at about 34 MHz. Since its impedance drops steeply thereafter a somewhat lower value should be used to allow for manufacturing tolerances. If you are using non VHF chokes then the frequency at which the maximum impedance is achieved for a given inductance can be substantially lower. These VHF chokes are relatively large (~30mm long). The substantial shunt capacitance of C6 may cause some difficulty in this circuit, tuning it out with a shunt inductor may help a little but the presence of R8 will make this lesseffective than it would otherwise be. C1 and C2 seem a little high for 34MHz operation using a resonator with an effective ESR of around 200 ohms or so. One of the Driscoll HF crystal oscillators may be more useful than a Copitts. Depending on the required stability an RF transformer connected between the collector and tank of such an oscillator may be used to extract a low noise current signal to drive a common base buffer transistor. Bruce ___ 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] Xtal-like Colpitts Oscillator
Jenny asked. Hi Everyone, I was hoping to get some words of wisdom on my oscillator that only oscillates in simulation! I have a MEMS device that resonates around 34 MHz at a given bias with Q of 100. You have already received some very good advice. You might also try a transistor with a higher ft. My personal experience is that it's easier to get an FET to oscillate in a colpits configuration. You won't be able to drive a 50 ohm load from an FET. A buffer of some kind will definitely be needed. Regards. Max. K 4 O D S. Email: [EMAIL PROTECTED] Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Music site: http://www.maxsmusicplace.com To subscribe to the fun with tubes group send an email to, [EMAIL PROTECTED] - Original Message - From: "Jenny Lee" <[EMAIL PROTECTED]> To: Sent: Monday, March 31, 2008 4:20 PM Subject: [time-nuts] Xtal-like Colpitts Oscillator Hi Everyone, I was hoping to get some words of wisdom on my oscillator that only oscillates in simulation! I have a MEMS device that resonates around 34 MHz at a given bias with Q of 100. I fit the impedance into a six-element equivalent model (similar to 4-element equivalent model of Quartz) and placed in a Colpitts configuration for the simulation. In the open-loop gain/phase plot, the peak barely passes 0 dB no matter what C1 and C2 I chose. For transient simulation, it does oscillates, but on a PCB, the circuit won't oscillate! I'm including the device impedance, circuit schematics and simulation results as an attachment. I've managed to oscillate 20 MHz device which has a higher maximum impedance than 34 MHz devices both in simulation and on a PCB - but for this I followed the guidelines of Colpitts for Quartz ranging at 10~20MHz. But above 20 MHz, for Quartz, overtones seem to be the way to go due to the manufacturing so I couldn't find any reference or circuits that operates Quartz for 30 MHz~50MHz ranges at a fundamental mode. I can only use fundamental mode for my device... I would really appreciate if you could share some of your experiences with Colpitts or any suggestions of what I can try to make it work... Thank you!-Jenny _ In a rush? Get real-time answers with Windows Live Messenger. http://www.windowslive.com/messenger/overview.html?ocid=TXT_TAGLM_WL_Refresh_realtime_042008 > ___ > 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] Xtal-like Colpitts Oscillator, time-nuts Digest, Vol 44, Issue 62
> Message: 2 > Date: Mon, 31 Mar 2008 21:20:43 + > From: Jenny Lee <[EMAIL PROTECTED]> > Subject: [time-nuts] Xtal-like Colpitts Oscillator > To: > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset="iso-8859-1" > > > Hi Everyone, I was hoping to get some words of wisdom on my > oscillator that only oscillates in simulation! I have . Are you sure it simulates? Transistor looks reverse biased, some odd looking values, Cout too small, 10nF more probable, L2 too large, a real component is probably well past self resonance at 34MHz, C7 too large. The direct drive into a 50 ohm load may be ambitious, I'd have expected a buffer amp on the oscillator output giving a higher load Z to your osc. Check the DC bias without a resonator, check the system as a buffer without the resonator or C1 fitted etc. Hope this helps. David ___ 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] Xtal-like Colpitts Oscillator
Jenny, In your schematic I'm assuming the uppermost transistor connection is the emitter. Your bias scheme is unlikely to exhibit its "paper" impedance at 34MHz. Any stray capacitance(s) can easily result in AC paths to ground lower than the L & R impedances in your circuit. The bias inductor will have a sef-resonant frequency well below your planned operating frequency. This inductor is probably useless. You need to modify your circuit model by adding a bunch of stray elements before it will be apparent why it doesn't work. Regards, Pete Rawson ___ 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] Xtal-like Colpitts Oscillator
Sorry for the previous noise... only zooming the image I saw that the supply voltage is -10V :) Regards, Javier -- Javier HerreroEMAIL: [EMAIL PROTECTED] HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17AFAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ 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] Xtal-like Colpitts Oscillator
Hello, The transistor is NPN and are you applying possitive supply voltage to the emitter and negative to the colector? Regards, Javier Jenny Lee escribió: > Hi Everyone, I was hoping to get some words of wisdom on my oscillator that > only oscillates in simulation! I have a MEMS device that resonates around 34 > MHz at a given bias with Q of 100. I fit the impedance into a six-element > equivalent model (similar to 4-element equivalent model of Quartz) and placed > in a Colpitts configuration for the simulation. In the open-loop gain/phase > plot, the peak barely passes 0 dB no matter what C1 and C2 I chose. For > transient simulation, it does oscillates, but on a PCB, the circuit won't > oscillate! I'm including the device impedance, circuit schematics and > simulation results as an attachment. I've managed to oscillate 20 MHz device > which has a higher maximum impedance than 34 MHz devices both in simulation > and on a PCB - but for this I followed the guidelines of Colpitts for Quartz > ranging at 10~20MHz. But above 20 MHz, for Quartz, overtones seem to be the > way to go due to the manufacturing so I couldn't find any reference or > circuits that operates Quartz for 30 MHz~50MHz ranges at a fundamental mode. > I can only use fundamental mode for my device... I would really appreciate > if you could share some of your experiences with Colpitts or any suggestions > of what I can try to make it work... Thank you!-Jenny > _ > In a rush? Get real-time answers with Windows Live Messenger. > http://www.windowslive.com/messenger/overview.html?ocid=TXT_TAGLM_WL_Refresh_realtime_042008 > > > > ___ > 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. -- Javier HerreroEMAIL: [EMAIL PROTECTED] HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17AFAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ 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] Xtal-like Colpitts Oscillator
Oh, I'm applying negative 10V to it -- drawn opposite... > Date: Mon, 31 Mar 2008 17:40:51 -0400> From: [EMAIL PROTECTED]> To: time-nuts@febo.com> Subject: Re: [time-nuts] Xtal-like Colpitts Oscillator> > The first problem that jumps immediately to my eye is> your power supply is backwards.> > -Chuck Harris> > Jenny Lee wrote:> > Hi Everyone, I was hoping to get some words of wisdom on my oscillator that only oscillates in simulation! I have a> > MEMS device that resonates around 34 MHz at a given bias with Q of 100. I fit the impedance into a six-element> > equivalent model (similar to 4-element equivalent model of Quartz) and placed in a Colpitts configuration for the> > simulation. In the open-loop gain/phase plot, the peak barely passes 0 dB no matter what C1 and C2 I chose. For> > transient simulation, it does oscillates, but on a PCB, the circuit won't oscillate! I'm including the device> > impedance, circuit schematics and simulation results as an attachment. I've managed to oscillate 20 MHz device which> > has a higher maximum impedance than 34 MHz devices both in simulation and on a PCB - but for this I followed the> > guidelines of Colpitts for Quartz ranging at 10~20MHz. But above 20 MHz, for Quartz, overtones seem to be the way to> > go due to the manufacturing so I couldn't find any reference or circuits that operates Quartz for 30 MHz~50MHz ranges> > at a fundamental mode. I can only use fundamental mode for my device... I would really appreciate if you could share> > some of your experiences with Colpitts or any suggestions of what I can try to make it work... Thank you!-Jenny > > _ In a rush? Get real-time answers with Windows Live> > Messenger. http://www.windowslive.com/messenger/overview.html?ocid=TXT_TAGLM_WL_Refresh_realtime_042008> > > > > > > > > > ___ 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. _ Windows Live Hotmail is giving away Zunes. http://www.windowslive-hotmail.com/ZuneADay/?locale=en-US&ocid=TXT_TAGLM_Mobile_Zune_V3 ___ 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] Xtal-like Colpitts Oscillator
The first problem that jumps immediately to my eye is your power supply is backwards. -Chuck Harris Jenny Lee wrote: > Hi Everyone, I was hoping to get some words of wisdom on my oscillator that > only oscillates in simulation! I have a > MEMS device that resonates around 34 MHz at a given bias with Q of 100. I fit > the impedance into a six-element > equivalent model (similar to 4-element equivalent model of Quartz) and placed > in a Colpitts configuration for the > simulation. In the open-loop gain/phase plot, the peak barely passes 0 dB no > matter what C1 and C2 I chose. For > transient simulation, it does oscillates, but on a PCB, the circuit won't > oscillate! I'm including the device > impedance, circuit schematics and simulation results as an attachment. I've > managed to oscillate 20 MHz device which > has a higher maximum impedance than 34 MHz devices both in simulation and on > a PCB - but for this I followed the > guidelines of Colpitts for Quartz ranging at 10~20MHz. But above 20 MHz, for > Quartz, overtones seem to be the way to > go due to the manufacturing so I couldn't find any reference or circuits that > operates Quartz for 30 MHz~50MHz ranges > at a fundamental mode. I can only use fundamental mode for my device... I > would really appreciate if you could share > some of your experiences with Colpitts or any suggestions of what I can try > to make it work... Thank you!-Jenny > _ In a rush? > Get real-time answers with Windows Live > Messenger. > http://www.windowslive.com/messenger/overview.html?ocid=TXT_TAGLM_WL_Refresh_realtime_042008 > > > > > ___ 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.
