OPERATIONAL-AMPLIFIER WITH 1-V RAIL-TO-RAIL MULTIPATH-DRIVEN OUTPUT STAGE

A bipolar operational amplifier (op amp) with a rail-to-rail multipath-driven output stage that operates at supply voltages down to 1 V is presented. The bandwidth of this output stage is as high as possible, viz. equal to that of one of the output transistors, loaded by the output capacitance. The output voltage can reach both supply rails within 100 mV and the output current is +/- 15 mA. The op amp is designed to be loaded by a 100-pF capacitor and the unity-gain bandwidth is 3.4 MHz at a 60-degrees phase margin. The voltage gain is 117 dB and the CMRR is 100 dB. The frequency behavior of the multipath-driven (MPD) topology has an improved performance when compared to that of previously presented low-voltage output stages. A figure of merit F(M) for low-voltage op amps has been defined as the bandwidth-power ratio.