An Integrated Per-Channel PCM Encoder Based on Interpolation

A novel technique called interpolation has been used to integrate a per-channel PCM encoder in a standard digital circuit technology. This encoder converts voiceband analog signals to both an oversampled 1-bit code and uniform PCM with μ-law companding noise. The circuit comprises approximately 550 integrated injection logic gates together with a resistive digital-to-analog converter, a voltage reference, and a simple differential amplifier. The encoder is part of a full PCM codec chip set suitable for a broad range of voiceband telecommunication applications.