The Effects of Direct and Indirect Compensation Techniques on the Specifications of Operational Amplifiers

Operational amplifiers are one of the fundamental building blocks of electronic circuits and their design quality is the main factor affecting the application areas and reliability. As well as gain, slew rate, and bandwidth, stability represents a crucial item determining the quality of operational transconductance amplifiers (OTA) covered in this study. All OTAs are designed to achieve the open-loop gain of 60dB and 3-stage opamp with indirect Miller compensation provides a slightly better phase margin as compared to the 2-stage configurations. On the other hand, the 2-stage opamp with zero-nulling resistor provides lower offset voltage, higher common-mode (CMRR) and power supply (PSRR) rejection ratios as well as improved gain bandwidth and slew rate. According to our results obtained for the open-loop gain of 60dB, the 2-stage amplifier with zero-nulling resistor provides better specifications.