A fundamental audio signal processing requirement is the control of gain; recent trends have been demonstrated towards control by electronic means. An inexpensive and viable means of gain control is the monolithic two quadrant multiplier, which can be configured for wide dynamic ranges (>80 dB) of signal handling and control, is capable of low distortion operation, fast response, and is flexible in its use. This paper deals with both the classic form of transconductance multiplier, and a more recent innovation, the Operational Transconductance Amplifier, which can be used as a multiplier and/or an amplifier. Considerations for optimized use in various audio signal processing functions is discussed, and representative circuitry is given.
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