Long description

This figure is a graph of gain G against normalised frequency. Two graph lines are shown, representing the Butterworth and Chebyshev filters.

The Butterworth line follows the shape seen in the previous figure: it starts at gain 1 for low frequencies, and curves down first gradually and then more steeply to reach a gain of 1 over root 2 at the cut-off frequency. After this, the line continues to descend steeply and then more gradually, until at high frequencies it approaches zero.

Below the cut-off frequency, the Chebyshev line oscillates between a gain value of 1 and a gain value of halfway between 1 and 1 over root 2. At the cut-off frequency, it drops very steeply and approaches a gain of zero at lower frequencies than the Butterworth line.