Class AB flipped voltage follower with very low output resistance and no additional power

Abstract

A modified version of the flipped voltage follower (FVF) with class AB operation and very low output resistance is presented. Instead of passing one of the large bidirectional output currents through the voltage following transistor, which considerably degrades the output resistance as in other variations, the proposed circuit maintains a constant current in this device and, hence, a very low output resistance. Complementary-type output transistors that depend on the same signal give the circuit the ability to provide large bidirectional currents at high frequency. The implementation only requires an additional resistor and one connection change, with no additional power consumption. Simulation and experimental results of the fabricated circuit in a 0.5μm technology show an output resistance of the proposed circuit of 12 Ω, with an enhancing factor of 60 with respect to previously reported variations.