The OP-421 quad low-power operational amplifier is a single-chip quad patterned after the OP-21 single operational amplifier. The PNP input stage allows the input common-mode voltage to include V-. Featuring a low power-supply current (150µA/section typical at 5V), the OP-421 offers a unique solution for designs requiring a combination of high function density, wide bandwidth, and low-power operation. Applications for the OP-421 include low-power active filters, battery-operated remote line filters, and signal preconditioning amplifiers. In addition, the ever-present problem of crossover distortion in low-power devices is eliminated by a unique double-buffered output section.