Understanding h-Parameters: hi, hf, hr, and ho

This document explains the meaning of h-parameters, specifically focusing on hi, hf, hr, and ho.

The image illustrates the h-parameter equations. Using these equations, we derive the following parameters:

Defining the h-Parameters

Here’s a breakdown of each h-parameter:

hi Parameter

• Definition: hi = (V1/I1)| V2=0
• Meaning: hi represents the input impedance of the transistor when the output is shorted (V2 = 0). Essentially, it’s the resistance seen at the input terminals under short-circuit output conditions.

hf Parameter

• Definition: hf = (I2/I1)| V2=0
• Meaning: hf signifies the short-circuit current gain. It’s the ratio of the output current (I2) to the input current (I1) when the output is shorted (V2 = 0). This parameter tells you how much the input current is amplified to produce the output current under shorted output conditions.

hr Parameter

• Definition: hr = (V1/V2)| I1=0
• Meaning: hr stands for the reverse voltage amplification with the input open-circuited. It’s the ratio of the input voltage (V1) to the output voltage (V2) when the input is open (I1 = 0). It indicates the feedback effect from the output to the input.

ho Parameter

• Definition: ho = (I2/V2)| I1=0
• Meaning: ho is the output admittance with the input open-circuited. It’s the ratio of the output current (I2) to the output voltage (V2) when the input is open (I1 = 0). Admittance is the inverse of impedance, so ho essentially represents the output conductance.