yeah..the gain expression for a common emitter circuit isSince this is a 'Homework help' forum, not a 'Homework done for you' one, show us your efforts so far.
Hey friends please help me on this..
q.1 what will be the gain expression of this circuit..?
q.2 what will be the equivalent resistance between point x and ground..with formula..??
q.3 what effect will be on gain if the value of Cfb1 is increased??
View attachment 101677
Thanks!!
I think so that you are talking about bootstrap action of Cfb1...which ceases the voltage gain of the circuit..For very small input signals Q1 won't conduct, so the voltage gain will be zero.
The gain expression of this circuit should be..Also try find a gain expression for this circuit
But this time the gain is negative so we do not "bootstrap" anything. And this is why we have a "Miller capacitor" this time.bootstrap action of Cfb1
The voltage gain without RF resistor is equal toThe gain expression of this circuit should be..
Av = {-β(Rc2//Rc1)/αRs} / 1+β(Rc2//Rc1)/αRf
Am I right??
yeah the feedback resistance appears to be decreased by (1-Av1) times due to miller effect..Notice the "miller effect" on RF.
So what effect will it make in the expression if Rf will be replaced by a capacitor..however text says that for a common emitter circuit miller effect acts as a degenerative feedback decreasing the voltage gain...And now if we add RF into the circuit the voltage gain will almost remains unchanged if Rc2 << RF.
But for Rs = 0Ω and RF>>Rc2 the gain will not change much. But with Rs > 0Ω and together with RF/(1 - Av) (decreased by Miller effect) form a voltage divider and this will decrease the voltage gain.however text says that for a common emitter circuit miller effect acts as a degenerative feedback decreasing the voltage gain...
Well, at first glance we can treat Cf as a frequency dependent resistor (Xc). And resistance of this resistor decreases with frequency.So what effect will it make in the expression if Rf will be replaced by a capacitor
Any change in gain expression if Rf is replaced by Cfb...??Avf ≈ - Rin*(Rs+Rin) * (Rc2||RF)/re' * alpha
Because I am thinking that if Cfb1 increases gain decreases because Xc decreases and if Xc decreases total impedance decreases ….But why you want to do such a thing ?
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