The SA571 Compandor is a versatile low cost dual gain control circuit in which either channel may be used as a dynamic range compressor or expandor. Each channel has a full-wave rectifier to detect the average value of the signal， a linerarized temperature-compensated variable gain cell， and an operational amplifier. The SA571 is well suited for use in cellular radio and radio communications systems， modems， telephone， and satellite broadcast/receive audio systems.

　　The SA571 compandor building blocks， as shown in the block diagram， are a full?wave rectifier， a variable gain cell， an operational amplifier and a bias system. The arrangement of these blocks in the IC result in a circuit which can perform well with few external components， yet can be adapted to many diverse applications.