Voltage buffer compensation using Flipped Voltage Follower in a two-stage CMOS op-amp

Abstract

In Miller and current buffer compensation techniques, the compensation capacitor often loads the output node. If a voltage buffer is used in feedback, the compensation capacitor obviates the loading on the output node. In this paper, we introduce an implementation of a voltage buffer compensation using a Flipped Voltage Follower (FVF) for stabilizing a two-stage CMOS op-amp. The op-amps are implemented in a 180-nm CMOS process with a power supply of 1.8V while operating with a quiescent current of 110µA. Results indicate that the proposed voltage buffer compensation using FVF improves the Unity Gain Frequency from 5.5MHz to 12.2MHz compared to Miller compensation. Also, the proposed technique enhances the transient response while lowering the compensation capacitance by 47% and 17.7% compared to Miller and common-drain compensation topologies. Utilization of FVF or its variants as a voltage buffer in a feedback compensation network has wide potential applications in the analog design space. Index Terms-Flipped voltage follower, frequency compensation, CMOS op-amps, voltage buffers, current buffers.

Design and Analysis of Flipped Voltage Follower for Different Aspect Ratio

“…They are capable of producing higher currents than that of bias current. Flipped voltage followers generally put on display superior results when kept in contrast to a basic conventional source follower due to their low output impedance [10]. Figure 6 shows the test bench schematic for the simulation purpose.…”