##### From Wideband Amplifier Design

It is useful to have two-port models available for the simplified transistor models introduced in Chapter 2. The model shown in Figure B-1 does not include any reference to *C _{jc}* or

*R*but these items are easily added later, and there are times you would want to do an analysis without them.

_{bb},*C*is included in the equation for

_{jc}*f*(and therefore

_{t}*T*) so the frequency response for the model has not been compromised. I have included

_{t}*R*because it is an important factor, and it is not always easily added. From this model, we want to derive the two-port

_{eb}*h*-parameter and the two-port

*s*-parameter model. We will begin with the

*h*-parameter model.

Figure B-1: A simplified model of the type we used extensively throughout the book.

In this model, *C _{?}* =

*T*and . Combining these two equations, we get . We will use these relationships in the following analysis.

_{t}g_{m}## B.1 *h*-PARAMETER TWO-PORT MODEL

The *h-*parameter two-port model is defined as

(B.1) | |

Multiplying this gives

(B.2) | |

and

To solve these, we use the following

(B.3) | |

By inspection, we see immediately that for the circuit of Figure B-1, *h* _{12} and *h* _{22} are both zero. Using Mathematica to solve node and loop equations derived from Figure B-1, we find that

(B.4) | |

Given the definition for *h* _{11}, we see immediately that

(B.5) |

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