100 KHz tuning fork crystal oscillator

[Andrew Holme]

I want to build a phase-lockable VCXO using one of these tiny 100 KHz tuning
fork (cylinder-type) crystals:

http://www.citizencrystal.com/images/pdf/k-cfs.pdf

I've got it to oscillate using the classic unbuffered CMOS inverter circuit
with a 5V supply, two 33pF loading caps, 1M feedback resistor and 100k
current-limiting resistor. This may still be too much drive - the datasheet
says 1uW max.

Is this a suitable circuit for these crystals? Can anyone recommend a
better circuit?

TIA

 

[Mark]

Check the input side of the inverter with a hi-Z 'scope probe.  If
it's significantly less than rail-to-rail and looks sinusoidal you
should be OK.

that was the easy part..

now how are you going to make it voltage controlled?

Mark

 

[Joerg]

that was the easy part..

now how are you going to make it voltage controlled?

'tis why varicap diodes were invented. But you'll have to use another
inverter (preferably a Schmitt) and some discretes to provide 15V or so.