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> > _______________________________________________>
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