Electronics

jason · Guest

Hello All

I am studying about Clapp LC oscillator.
Given below link is the circuit of interests
http://www.geocities.com/jason_class/ClappLC.jpg

May I know how do we calculate by hand if this circuit gonna oscillate
or not?

I learnt in lecture that I must find Av multiply by beta(feedback
factor). Av is always given by gm multiply by R efficient , which is
gmReff
Reff is the sum of series and parallel resistances of all emitter
resistance, ac emitter resistance , load resistance and also reflected
resistances from the tap of capacitors. Emitter is mentioned here
because I learnt about bipolar transistor configuration.

For the circuit in the link given, I do not understand why the same
approach is use?
Why we can use gmReff as the Av since it is a common drain
configuration? Is it because we have already sum all the net
resistances in Reff , therefore we can use gmReff as the Av?

So for other type of configuration of mosfet such as common gate and
common source? We can use the same Av=gmReff ?
If possible show me the correct way of checking if the circuit can
oscillate by manual calculation..at least the steps or methodology.
Really appreciate your help in advance.

Kindly enlighthen

rgds and thanks
Jason

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