# CHAPTER 13

*Frequency Response*

**IN HIS CHAPTER**

**13.1** Introduction

**13.2** Gain, Phase Shift, and the Network Function

**13.3** Bode Plots

**13.4** Resonant Circuits

**13.5** Frequency Response of Op Amp Circuits

**13.6** Plotting Bode Plots Using MATLAB

**13.7** Using PSpice to Plot a Frequency Response

**13.8** How Can We Check … ?

**13.9 DESIGN EXAMPLE**—Radio Tuner

**13.10** Summary

Problems

PSpice Problems

Design Problems

## 13.1 *Introduction*

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:

- The ratio of the amplitude of the output sinusoid to the amplitude of the input ...