Category: CDS Glossary

Identifiers: B H

Questions

• bandwidth

• bandwidth
  Submitted by: waydo
  Submitted on: November 10, 2004
  Identifier: B

  Bandwidth is the frequency at which the *closed-loop* transfer function has a gain of 1/2 its DC value. That is, if G(s) is the closed-loop transfer function, the bandwidth is the frequency w at which |G(jw)|/|G(0)| = 1/2. You may see it mentioned that the bandwidth is the frequency at which the *open-loop* transfer function has gain 1 (0 dB), but this is only a useful approximation for design purposes. The approximation rougly works because the closed-loop gain is about 1/(1+1) = 1/2 when the open-loop gain is 1, but an error is introduced by the phase of the open-loop transfer function at the crossover frequency.

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