Hi,
I have some problem in following circuit please help me.

Determine Voltage Gain (Av) of Common Emitter amplifier circuit with and without bypass capacitor.
values:
1. RC = 3.3k ohm
2. RE = 680 ohm
3. r'e = 30 ohm

I know Rc is Collector Resistance and RE for Emitter Resistance, but what is r'e?

And please tell me following formulas are correct?
Av = Rc/Re (calc with bypass capacitor)
Av=Rc/r'e+Re (calc without bypass capacitor)
Thanks

 

Your equation looks OK.
And as for 'r'e = 1/gm = VT/Ic = 26mV/Ic

http://whites.sdsmt.edu/classes/ee320/notes/320Lecture14.pdf