A monolithic analog compandor
Craig C. Todd · IEEE Journal of Solid-State Circuits · 1976
Describes a bipolar IC analog dynamic range compandor. The approach taken to implement the compressor and expandor functions is discussed, and the active full wave rectifier and variable gain cell are described in detail. Performance easily exceeds telecommunications requirements and is suitable for use in high quality audio systems. The full wave rectifier has excellent accuracy over a 60-dB dynamic range. The variable gain element offers low distortion (<0.1 percent) attenuation with high signal to noise ratio (90 dB). Ion-implanted resistors have been used for lower temperature sensitivity.