Hi, Qadeer,
Quote:My only conern is that how do we decide that how much initial current would the xtal get on actual silicon.
Don't worry about the initial condition of the actual silicon. If the AC analysis proves that your xtal osc has enough gain at the 360
o phase shift, the actual silicon must oscillate because there is noise in the circuit. The noise makes the xtal osc deviate from the balance point and initiates the oscillation, which is different from the SPICE transient simulation.
There isn't any noise in transient simulation. Thus sometimes you have to initiate the oscillation using an initial current for inductor, or kick the oscillator with a small pulse. In one word, the xtal oscillator needs some energy to start. But it is depends on your circuit that the xtal osc needs the initial current or so. Sometimes the xtal osc starts oscillating without any initial condition because the SPICE transient simulation has small intrinsic noise due to the iteration and integration algorithm. For example, it is easier to start for method=trapzoid than method=gear.
Do you have any other concerns?
Best regards,
Yawei