##### 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 bb, but these items are easily added later, and there are times you would want to do an analysis without them. C jc is included in the equation for f t (and therefore T t) so the frequency response for the model has not been compromised. I have included R eb because it is an important factor, and it is not always easily added. From this model, we want to derive the two-port 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 tg m and . Combining these two equations, we get . We will use these relationships in the following analysis.

## 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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##### Topics of Interest

The following was contributed by Dr. Allen Podell (he teaches Advanced Wireless Microwave Techniques at Besser Associates and is an expert in microwave engineering). It is a discussion of how T-coils...

2.7 A LITTLE TOO SIMPLE; ADD BACK R eb AND C jc Unfortunately, the previous derivation is a little too simplistic to model the actual emitter follower when loaded with a capacitance. In particular,...

5.5 Simplified Model Equations For Type 1 collisions there are no changes with respect to the exhaustive model and we must define a value of each degradation parameter for each input. Therefore, the...

OVERVIEW The concept of a two-port was informally introduced in Chapter 5 to provide a common framework for the study of transformers and amplifiers. We now reexamine this concept from a more general...

10.5 HYBRID OR h-PARAMETERS If I 1 and V 2 are taken as the independent variables, the two-port equations may be written as The constants h 11, h 12, h 21, and h 22 are called the hybrid (or h)...

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