Oh, I'm applying negative 10V to it -- drawn opposite... > Date: Mon, 31 Mar
2008 17:40:51 -0400> From: [EMAIL PROTECTED]> To: [email protected]> 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?
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> > > > >
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