An offset-compensated wide-bandwith CMOS current feedback operational amplifier

The low-input offset voltage is considered as an important aspect of the performance of an amplifier especially when signals are in the range of few hundreds micro Volts. The aim of this paper is to describe a new CMOS current-feedback operational amplifier with an on-chip current-mode input offset voltage compensation. This voltage is due to the mismatch between transistors threshold voltages. In order to reduce the offset voltage, we vary the bias currents of the input buffer as a function of the detected error. Simulation results of the compensated CFOA, using 0.18mum CMOS process parameters, show a: 50% reduction of the input offset voltage, 71 dB open loop gain, 160 MHz bandwidth, and power consumption less than 1.5 mW from 1.8 V supply voltage.