A programmable gain/loss circuit

A general-purpose gain/loss circuit is described. Its function is controlled by an 8-b digital word. It provides up to 256 0.1-dB steps in gain or loss. The circuit has two modes of incremental gain/loss steps (two sets of gain/loss values for bits in the control word). A ninth bit selects between gain and loss. The IC has three digital interfaces: serial, parallel clocked input, and parallel fixed input. The chip is fabricated in a 3-μm CMOS n-well process. It requires a ±5-V power supply, and for maximum gain of 25.5 dB, the 0.1-dB large-signal bandwidth is 260 kHz.