[time-nuts] Xtal-like Colpitts Oscillator

[Chuck Harris]

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 
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