An Ultra-Low-Voltage Bulk-Driven Analog Voltage Buffer with Rail-to-Rail Input/Output Range

Abstract

This paper presents a low-voltage high driving capability rail-to-rail Class-AB CMOS bulk-driven (BD) operational transconductance amplifier (OTA) for analog voltage buffer with minimal current consumption. The proposed OTA design consists of adaptively biased Class-AB differential input stage to improve the effective transconductance and adaptive load relying on nonlinear current mirrors, configured in partial positive feedback mode to enhance the overall gain. In addition, because of adaptive bias and load configuration, the load-driving capability of OTA increases for a large change in differential input. The circuit is designed using UMC 65-nm CMOS process node and is operated at supply voltage of 0.5 V with a standby current consumption of 4.25 $$\upmu $$μA. Simulation results show that the buffer based on the proposed BD-OTA achieves an average slew rate of 93.2 mV/$$\upmu $$μs for a capacitive load of 100 pF, which is nearly 29 times that of conventional OTA with 13$$\%$$% increment in quiescent power dissipation.