Bypass Capacitor sets the gain and AC

[walters]

Thanks Skyhigh

This is it:
The emitter resistor sets the lower limit where the output AC signal can swing. However with the use if a bypass capacitor, the lower limit is extended, thus giving the output signal a larger AC swing.

The emitter resistor in parallel with the capacitor = reactance
so its Frequency based:
The Bypass capacitor is a "Frequency Based" gain because of reactance on the emitter resistor so the AC swing getting bigger only at certain frequencys
and limited at others

 

[SkyHigh]

Reactance of the capacitor, which is variable to frequency, sets the impedance. The resistor doesn't have reactance.

 

[SkyHigh]

walters,

if you think the information i provided is helpful, perhaps you can do me a favour by increasing my help count. cheers!

 

[walters]

Yea thanks alot skyhigh for helping me i need it

 

[A.Anand Srinivasan]

since you are talking about bypass capacitor to Emitter i think you are talking about CE configuration here you have to understand just the change in the value of the emitter resistance for AC which leads to difference in the gain calculated by Rc/Re...

 

[electronics_kumar]

for only emitterresiatance circuit,
voltage gain=collector resistance/emitter resistance
for emitter resistance along with capacitor,
Volt.gain=transconductancex collector resistance


actual expression for voltage gain is
( transconductance x collector resistance)/(1+transconductance x emit.resistance)

for the first case it will become " collector resistance/emitter resistance" since
(1<<<<transconductance x emit. resistance)

for the second case emit .resitance will be surpassed by capacitance ,so it will become as i mentioned above