A power-efficient, low-distortion variable gain amplifier consisting of coupled differential pairs

A variable gain amplifier incorporating a plurality of coupled differential pairs has been designed in a bipolar technology. By applying variable offset voltages to these differential pairs, the overall gain of the system can be varied. The linear input region is inversely proportional to gain, making the amplifier very well suited for automatic gain control circuits. Furthermore, the gain of the proposed amplifier is 0-25 dB, the signal bandwidth is 35 MHz, and the output IP3 is 24-30 dBm. It operates from a 5 V power supply and dissipates 40 mW. The active chip area is 0.15 mm/sup 2/ in a 1 /spl mu/m bipolar technology.