Low-Power High-Drive CMOS Operational Amplifiers

Low-power CMOS op amps with high-drive capability and good settling characteristics are described. One circuit, occupying 150 mils² of active area and consuming 1 mW of power drives a capacitive load of up to 150 pF with greater than +-2.5 V/µs slew rates and less than 3.5 µs settling time to 0.1 percent. A somewhat larger circuit drives low-resistance (e.g., 600 Omega) and high-capacitance (1000 pF) loads with better slew rates and settling time. These circuits are suitable for applications in such systems as charge-redistribution codecs and switched-capacitor filters.