カスケードオペアンプ

Operational Amplifiers can be connected in a cascade - one after another in linear sequence without altering their input-output relationships due to their infinite input resistance and zero output resistance.

In a cascaded system, each amplifier is known as a stage, and the output of one amplifier drives the following amplifier.

The input signal is successively amplified by the gain of each stage, resulting in an overall larger gain equal to the product of each amplifier's gain.

The total gain is distributed among multiple stages, with each stage having less gain than if a single op amp was used. Since the gain-bandwith product remains constant for each op amp, this distribution increases the bandwidth for each stage, leading to an overall increase in bandwidth.

In television circuits, tuned RF amplifiers make use of cascaded op amps. They amplify weak signals and improve input and output impedance matching, delivering high-quality audio and video signals.

The cascaded op amp circuit should be designed such that the individual gains do not saturate the signal in the various stages of the cascade.