Low-power high-drive CMOS operational amplifiers

Low-power CMOS op amps with high-drive capability and good settling characterists are described. One circuit, occupying 150 sq mils of active area and consuming 1 mW of power drives a capacitive load of up to 150 pF with greater than + or - 2.5 V/microsec slew rates and less than 3.5 microsec settling time to 0.1 percent. A somewhat larger circuit drives low-resistance (e.g., 600 ohms) and high-capacitance (1000 pF) loads with better slew rates and settling time. These circuits are suitable for applications in such systems as charged-redistribution codes and switched-capacitor filters.