Peter L. Peres email (remove spam text)
after following all this discussion, I've come to a practical idea. I
have worked with stable oscillators before, and I'd like to see how stable
a PIC can be made using easily bought components. I propose to exchange
data on this on the list.
I have the following ideas:
1) Temperature stabilization. The two obvious ways are crystal oven and
thermistor controlled varactor. The oven is often ruled out due to power
constraints, but the one-thermistor method could be used. Commercial
expensive thermistors are ruled out. So I'd like to see how a transistor's
2.2 mV/K could be used for this while being itself the varicap (Ccb ?).
Other ways ?
2) Amplitude stabilization. The purpose is to reduce the drive level
measured at the Xout pin as much as possible without causing malfunction
of the PIC. This is to be achieved by reducing the coupling from the Xout
to the frequency selective element in a closed loop. The usual way is
metering and negative feedback applied to a linear gain controlling
element. This could be a PIN diode, a Si diode, or other ? Two desirable
side effects: Power consumption should be reduced, and RFI also. How to do
this (without using an op-amp or special parts) ?
In reply to: <01BE00CE.2CB84790@JOHN_WKST1>
See also: www.piclist.com/techref/index.htm?key=crystal+tutorial
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