I want to design a crystal oscillator (pierce) but I'm having trouble. Proposed oscillation frequency is around 39 MHz and I used crystal L~4mH C~4.1fF R~10ohm; Co~2pF
C1,C2=20pF (shunt cap for drain to GND & gate to GND)
Feedback resistor ~ 1 Mohm; Vdd~1.5V Transistor gm~80u
However, my oscillator input/output settles to same voltage, and does not oscillate.
When I change crystal cap to 200 fF then it starts oscillation.
- Can crystal motional cap affect to oscillation?
- What is the cause for non oscillating?