gain in class A signal amplifier

alimash

Joined Oct 12, 2016
67

"In the DC only conditions,
the gain of the amplifier was dependent on the ratio of RL to RE"
1-does this mean:Vout/Vin=-RL/RE
2-how can i conclude this mathematically?

dannyf

Joined Sep 13, 2015
2,197
1-does this mean:Vout/Vin=-RL/RE
Yes, if Rl includes all the impedance the collector sees - in this case, RL // C4 // input impedance of the next stage, to name a few. Similarly, Re = Re // C3.

2-how can i conclude this mathematically?
Ie ~= Ic and (delta) Ie = Vin / (RE//C3)

alimash

Joined Oct 12, 2016
67
if you can explain more, i will appreciate it because i did not understand it perfectly?
are you saying that in dc condition:
Vout=-RL.IC and Vin=RE.IC
so gain=-RL/RE
where those tow equation come from?
Thank

alimash

Joined Oct 12, 2016
67
what i mean is:
the calculations in small signal model lead to this result:
Av=-(beta*RL)/r (mid band gain)
where "r" is the dynamic resistance
but i keep seeing the above expression in many references
what does it refer to ?