Question

How do we determine the value of the hybrid parameter h21 in a high frequency T model?

(a) h21 = I1 / I2

(b) h21 = V1 / V2

(c) h21 = I2 / I1

(d) h21 = V2 / V1

The question was asked by my college professor while I was bunking the class.

This interesting question is from The High Frequency T Model in portion High Frequency Transistor of Electronic Devices & Circuits

Answer 1

Right choice is (c) h21 = I2 / I1

To elaborate: To calculate the value of h21 high frequency T model, we short circuit the output terminal so the output voltage V2 equals zero. Hence the equation for hybrid parameters becomes, I2 = h21I1 + 0. Therefore, h21 = I2 / I1.