# common collector

Discussion in 'Homework Help' started by amangupta1219, Oct 30, 2012.

1. ### amangupta1219 Thread Starter New Member

Oct 18, 2012
19
0
for the common collector configuration shown i need to find the voltage gain.
The voltage gain formula is AV = (β+1)(roll RE)/(rπ+(β+1)(roll RE)
But in the circuit RE is absent . So how do we consider it ??
Nothing is given about the current source.

from the circuit theory i know that the internal impedance of a current source is very high (am i correct ?).

So in this case how do we relate it ?

File size:
172.4 KB
Views:
39
2. ### panic mode Senior Member

Oct 10, 2011
1,328
305
current source is considered high impedance (ideally infinite).
i don't know what is (roll RE) and how you got it so I'm attaching my version.
if something does not show up in the circuit, gets removed from equation.

File size:
23 KB
Views:
32
• ###### MOS.gif
File size:
23.7 KB
Views:
23
Last edited: Oct 30, 2012
amangupta1219 likes this.
3. ### amangupta1219 Thread Starter New Member

Oct 18, 2012
19
0
it is early resistance ro parallel with RE . I don't know how to do formatting here

4. ### Jony130 AAC Fanatic!

Feb 17, 2009
3,990
1,115
Use a small signal analysis and find the voltage gain.
But for ideal case - ideal current source and R_load = ∞ the voltage gain is equal 1V/V

amangupta1219 likes this.