High current operational amplifier with current limiting protection circuit

Abstract

In this work, a class-AB operational amplifier is to be presented, which is developed in a 0.5 μm CDMOS technology. The proposed amplifier is composed of a folded cascade input stage and a class-AB output stage. Owing to the special design of the operational amplifier, the robustness of the whole circuit has been enhanced. The proposed system can drive a wide resistance load range from 10 Ω to 100 kΩ with a 10 pF capacitance load without distortion and stability problems. In addition, a current-limit technique that stems from the design of a low dropout linear regulator is adopted to protect the output stage of the operational amplifier from being damaged by a huge transient current under unexpected conditions (when the output terminal is shorted to ground or V DD). Measurement results show that the maximum output current is nearly 390 mA with an 800 mA DC current limiting protection circuit on the single 5 V power supply at room temperature. This design can stably work at the industrial temperature range from −40 to 125°C. What is more, the total static current consumption of the whole circuit is 624 μA and the chip area is 0.419 mm2.