H - Parameter model :-

• The transistor's equivalent circuit can be dram using simple approximation by retaining its necessary features.
• These equivalent circuits will assist in analyzing transistor circuits simply and quickly.

Two port devices & Network Parameters:-

• A transistor can be treated like a two part network. The terminal behaviour of any type of two part network can be specified through the terminal voltages V₁ & V₂ at parts 1 & 2 correspondingly and current i₁ and i₂, entering parts 1 & 2, correspondingly, as displayed in figure.

                                       Figure: Two port network

• Of these 4 variables that are V­₁, V₂, i₁ and i₂, two can be chosen as independent variables and the remaining two can be expressed in terms of these independent variables. This directs to various two part parameters out of which the following three are more significant.

a)      Z - Parameters (or) Impedance parameters

b)      Y - Parameters (or) Admittance parameters

c)      H - Parameters (or) Hybrid parameters.