Noise reduction circuit with a main signal path and an auxiliary signal path having a high-pass filter characteristic

摘要

A noise reduction circuit includes a main signal path and an auxiliary signal path having a high-pass filter characteristic. The noise reduction circuit may be used as a compression circuit or an expansion circuit in conjunction with a transmitter or a receiver, respectively. The auxiliary signal path includes a voltage dividing circuit, a voltage-to-current coverting circuit; a differential amplifier, and a voltage buffer connected between an input terminal and an operational amplifier. The main signal path is constituted by a resistance connected between the input terminal and the operational amplifier. The noise reduction circuit improves precision by eliminating the influence of absolute value variation of resistance which can occur in integrated circuit fabrication.