Thus far our analysis of AC circuits has revolved around constant frequency sources. However, if we were to hold the amplitude of the source AC waveform constant and vary the frequency, we are able to determine what is known as the "frequency response".

## Definition:

The frequency response completely describes the steady-state behavior of a sinusoidal waveform as a function of frequency. Essentially we are looking for a change in circuit behavior due to a change in signal frequency.

## Applications:

Analysis of a circuit's frequency response is important in the design of filters used in the blocking of unwanted frequencies and the passing of desired ones. (ie: separating broadcast frequencies.)

## Concepts covered in the following pages:

- Analysis using the transfer function.
- Analysis using Bode plots.
- Series and parallel resonant circuits.
- Resonance, quality factor, cutoff-frequency and bandwidth.
- Filters and network scaling.

Let's begin by examining the Transfer Function...