Question

For the circuit given below, the value of z22 parameter is ____________

(a) z22 = 20 Ω

(b) z22 = 25 Ω

(c) z22 = 30 Ω

(d) z22 = 24 Ω

I had been asked this question during an interview.

This intriguing question originated from Advanced Problems on Two Port Network topic in section Two-Port Networks of Network Theory

Answer 1

The correct option is (c) z22 = 30 Ω

The explanation: z11 = \(\frac{V_1}{I_1}  = \frac{(20+5)I_1}{I_1}\) = 25Ω

V0 = \(\frac{20}{25}\)V1 = 20 I1

-V0 – 4I2 + V2 = 0

Or, V2 = V0 + 4I1 = 20I1 + 4I1 = 24 I1

Or, z21 = \(\frac{V_2}{I_1}\) = 24 Ω

V2 = (10+20) I2 = 30 I2

Or, z22 = \(\frac{V_2}{I_1}\) = 30 Ω

V1 = 20I2

Or, z12 = \(\frac{V_1}{I_2}\) = 20 Ω

∴ [z] = [25:20; 24:30] Ω.