1. Chapter 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. The sinusoidal frequency response (or, simply, frequency response) of a circuit provides a measure of how the circuit responds to sinusoidal inputs of arbitrary frequency. The frequency response of a circuit is a measure of the variation of a load-related voltage or current as a function of the frequency of the excitation signal.

3. A circuit model Thévenin equivalent source circuit

4. Complete equivalent circuit

5. V L ( jω) is a phase-shifted and amplitude- scaled version of V S ( jω).

8. Filters Low-Pass Filters A simple RC filter

10. Magnitude and phase response plots for RC filter

11. High-pass filter High-Pass Filters

12. Frequency response of a high-pass filter

13. Bandpass Filters, Resonance, and Quality Factor RLC bandpass filter

15. Frequency responses of RLC bandpass filter

16. Resonance and Bandwidth

17. (a) Normalized magnitude response of second-order bandpass filter; (b) normalized phase response of second-order bandpass filter

18. Bode Plots Frequency response plots of linear systems are often displayed in the form of logarithmic plots, called Bode plots, where the horizontal axis represents frequency on a logarithmic scale (base 10) and the vertical axis represents the amplitude ration or phase of the frequency response function. In Bode plots the amplitude ratio is expressed in units of decibels (dB), where

20. Bode plots for low-pass RC filter; the frequency variable is normalized to ω/ωο. (a) Magnitude response; (b) phase response

21. Bode plots for high-pass RC filter. (a) Magnitude response; (b) phase response