OVERVIEW

Having mastered the tools of circuit analysis, we now wish to apply them to the study of two systems of great practical interest, namely, the transformer and the amplifier, the workhorses of electrical and electronic engineering. The former finds application especially in the handling of electrical power, the latter in the processing of electronic information. While Chapters 1 through 4 have, of necessity, emphasized analysis, Chapters 5 and 6 shift attention to applications using analysis as a tool for understanding the function of a circuit.

Both transformers and amplifiers belong to a class of circuits known as two-port circuits, or two-ports for short. One port, called the input port, serves as point of entry of energy or information coming from a circuit upstream called the source. The other port, called the output port, serves as point of exit of energy or information for delivery to a circuit downstream called the load. The situation is depicted in Figure 5.1.

Figure 5.1: Two-port and its typical interconnection.

Perhaps the simplest two-port examples are the voltage and current dividers, whose function is to attenuate a signal coming from an external source. A far more sophisticated two-port example is a hi-fi audio amplifier, which accepts a weak input signal from a transducer source and magnifies it to produce the powerful output signal required to drive a loudspeaker load.

In light of Section 4.1, both the input and output ports exhibit individual i-v characteristics,...