Fully differential high-gain high-GBW operational amplifier in 250 nm BiCMOS process

Abstract

Design of high-speed analog-to-digital converters, high-frequency active filters and other analog signal processing systems with high demands to heir constituent units parameters, requires operational amplifiers with high dc-gain and high unity gain frequency. In developing operational amplifiers with unity gain frequency of several gigahertz and phase margin of more than 600 in the CMOS process, several problems arise. The main problem of MOS transistors using is in reducing the high frequencies gain, as well the large phase shifts caused with high gate capacitance. Application of bipolar transistors allows obtaining larger high frequency gain with much smaller consumption currents. In the article a fully differential amplifier in 250 nm BiCMOS process is proposed, which provides at capacitive load of 1 pF the unity gain frequency of 2.536 GHz, and the DC-gain 135 dB in the temperature range −40…85°C with current consumption of 14 mA.