A monolithic companding D/A converter

COMPANDED PULSE CODE MODULATED (PCM) transmission of voice signals has become standardized through widespread use of the Bell system p-law and the CCITT** A-law transfer characteristics. Until now, all codecs (eoder/decoders) for these communication systems have been fabricated in either discrete or hybrid form and have been relatively expensive. This paper will present a newly developed monolithic digital-to-analog converter specifically designed for compression and expansion of signals according to the existing PCM standard. This converter, however, is not limited to PCM communication, but may be used in other areas such as data acquisition, servo controls, data recording, telemetry, voice synthesis, log attenuation, secure communications, sonar, and many other applications which require a 12-bit plus sign dynamic range and the convenience of an 8-bit digital code