Transistor as an Amplifier

Common base amplifier

In this type amplifier, base to emitter junction is forward bias whereas to collector is reverse bias.

Transistor parameter

Current gain =∝ =I_C/L_E

Voltage gain = A=v₀/v_i= I_CR_out/L_ER_in

=Current gain x Resistance gain

Where R_out=Resistance of the output circuit

R_in=Resistance of the input circuit

Power gain=∝² x Resistance gain

Common emitter amplifier

Current gain β= I_C/L_B

Voltage gain (Ac)= Current gain x Resistance gain

Power gain β²= x Resistance gain

Resistance gain= R_out/R_in

Common collector amplifier

In this type amplifier, collector to base junction is forward bias whereas collector to emitter is reverse bias.

Transistor parameters

Current gain=γ= I_E/L_B

Voltage gain= A=v₀/v_i= I_ER_out/L_BR_in

=Current gain x Resistance gain

Where R_out=Resistance of the output circuit

R_in=Resistance of the input circuit

Power gain= γ² x Resistance gain