For the circuit shown in the below figure find Av Rir and Ro

For the circuit shown in the below figure, find Av, Rir and Ro. Also, find Ri (input) Ro (output), and voltage gain Av. 21 V 3 k2 90 k2 VCE BE 10 km Zvo vin (An) 45 k2 IE

Solution

In the above circuit the given values are R1 = 90K, R2 = 45K, Rc = 3K, Re = 2K, RL = 10K and Vcc = 21V

The above circuit is a CE amplifier with Voltage-Divider bias.

The Input Impedance Ri = R_B parallel to h_ie

Wher R_B = R1 ll R2 = R1 x R2 / (R1 + R2) = 90 x 45 / 135 = 30K

Ri = R_B parallel to h_ie = R_B h_ie / R_B + h_ie = 30hie / 30 + hie

2. Outimpedance Ro = Rc // RL = Rc x RL / Rc + RL = 3x10/13 = 2.3K ohms

3.Voltage gain Av = -hfe Rc / hie = -3000hfe / hie

4. Current gain Ai = -hfe(R_B / R_B + hie) = -hfe (30000/30000+hie)