A GaAs HBT monolithic microwave switched-gain amplifier with +31 dB to -31 dB gain in 2 dB increments

A GaAs/AlGaAs heterojunction bipolar transistor (HBT) monolithic 5-bit digital gain control amplifier is presented that was developed for use in electronic warfare receivers. The digital-control variable-gain amplifier is composed of five gain/attenuation stages and an output buffer. A current-mode logic (CML) switch selects either the high-gain differential pair or the attenuating differential pair for each of the five stages. Distributing the gain into +or-16 dB, +or-8 dB, +or-4 dB, +or-2 dB, and +or-1 dB increments achieves +or-31 dB programmability in 2-dB increments from DC to 2.25 GHz, with less than 1.6 dB RMS gain error across the band. The switched gain amplifiers were fabricated with a 3- mu m-emitter, self-aligned base ohmic metal (SABM) HBT IC fabrication process. The chip consumes 1.3 W and measures 1.2 mm*2.2 mm.<>