# BJT single stage amplifier we write gm=Ic/VT

 P: 410 BJT single stage amplifier we write gm=Ic/VT Yes you should use 2*Vt if you want to find voltage gain. The small signal gain for CE amplifier is equal to $\Large \frac{Vout}{Vin} =-\frac{Rc (\beta 1+\beta 2+\beta 1 \beta 2)}{(1+\beta 1) (re1+re2+re2 \beta 2)}$ Where re1 ≈ 1/gm1 re2 ≈ 1/gm2