IN HIS CHAPTER
Consider the experiment illustrated in Figure 13.1-1. Here a function generator provides the input to a linear circuit and the oscilloscope displays the output, or response, of the linear circuit. The linear circuit itself consists of resistors, capacitors, inductors, and perhaps dependent sources and/or op amps. The function generator allows us to choose from several types of input function.
Suppose we select a sinusoidal input. The function generator permits us to adjust the amplitude, phase angle, and frequency of the input. First, we notice that no matter what adjustments we make, the (steady-state) response is always a sine wave at the same frequency as the input. The amplitude and phase angle of the output differ from the input, but the frequency is always the same as the frequency of the input.
After a little more experimentation, we find that at any fixed frequency, the following are true: