# [HELP] Designing Commom Emitter 2N3904

Discussion in 'Homework Help' started by WiseToad, Apr 22, 2014.

Jul 8, 2013
1
0

My prof just assign my class a new assignment to design a BJT amplifier with common emiter configuration.

the circuit have to met these criteria below :
o> Using 2n3904 transistor
o> Have 600 ohm input resistance
o> Have 300 ohm ouput resistance
o> Have -15V amplifying power (Av)

The assignment is due the day after, but i need to test and print the circuit ont the pcb tomorow.

I have done some calculation and simulation and i got nothing.

2. ### crutschow Expert

Mar 14, 2008
13,501
3,375
Show your calculation and simulation. We don't do the work for you.

This should help.

What is the gain required?

3. ### PRS Well-Known Member

Aug 24, 2008
989
35
The input resistance is r(pi) in parallel with R1 and R2. Find the equation for r(pi) and work with it. The output resistance is the collector's resistance (about 100kohms) in parallel with Rc. What does this suggest?

You've been given some funny parameters. 15v/v is not much gain and 300 ohms output resistance is very low, and for that matter 600 ohms input resistance is rather low. Are you sure you have the numbers right?

4. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,504
512
Gain is not measured in volts.