TABLE OF CONTENTS The manner in which the ac response varies as a function of frequency is called the frequency response. This response is of paramount importance in a variety of disciplines such as communications, signal processing, and control. The frequency response can be predicted mathematically using the network function H( s). To this end, we first derive H( s) using s-domain techniques; then we calculate it on the j ? axis by letting
The frequency response can be visualized graphically by plotting the magnitude H( j ?) and phase 
versus ?. It can also be observed experimentally by subjecting the circuit to an ac signal of fixed amplitude X m and phase angle ? x but variable frequency ?. The amplitude Y m and phase angle ? y of the response are measured with the oscilloscope for different values of ?, and the magnitude H( j ?) = Y m/ X m and phase 
are then plotted point by point versus ?.
The effect of letting s ? j ? is illustrated in Figure 14.5 for the magnitude case. As we know, H( s) can be calculated anywhere in the s plane. However, when we seek the ac response, we confine ourselves to the j ? axis, indicating that...
