A Low-Power Wideband dB-Linear Variable Gain Amplifier With DC-Offset Cancellation for 60-GHz Receiver

This paper presents a two-channel (I+Q) variable gain amplifier (VGA) for low power 60-GHz wireless receiver. The VGA consists of four-stage gain cells, an efficient DC-offset cancelling circuit and an output buffer for test purposes. To achieve wide bandwidth and low power consumption, a modified Cherry-Hooper amplifier gain cell is used. With a tunable transistor and its parasitic capacitance, a dB-linear characteristic and a flat gain response are achieved without any additional exponential circuit. The DC-offset is cancelled effectively with two proposed feedback loops. The measurement results show that the VGA achieves a gain range of 6 to 44 dB, an OP1dB of 1 dBm, and a 3-dB bandwidth of over 1 GHz with an excellent flat gain response. Fabricated in a 65-nm CMOS technology, the two-channel VGA core occupies a silicon area of only 0.055 mm2 and consumes only 10 mA from a 1.2 V power supply.