A compensation strategy for two-stage operational transconductance amplifiers based on zero splitting

Abstract

This paper presents a compensation method in which the phase margin and unity gain bandwidth of an Operational Transconductance Amplifier (OTA) is improved by addition a(n) active/passive resistive to the frequency compensation circuit. This improvement is achieved without changing the power consumption of the OTA. Based on the proposed strategy, three different compensation structures including RHC, RRHC and composite are introduced. Simulation results in a 180nm CMOS technology show that for power consumption of about 6 mW and DC voltage gain of 100 dB, the conventional Hybrid Cascode Compensation structure shows unity gain bandwidth (UGBW) and phase margin (PM) of about 310 MHz and 60°, respectively. For the same power and DC voltage gain, the proposed RHC and RRHC structures demonstrate UGBW/PM of about 405 MHz/60° and 425 MHz/65°, respectively. The proposed composite structure with active compensation path shows DC voltage gain of 105 dB, UGBW of 345 MHz, and PM of 60° while its power consumption is about 6 mW.