A high-performance all-enhancement NMOS operational amplifier

An NMOS operational amplifier has been designed and fabricated using only enhancement mode MOSFETs in a circuit that employs a novel feedforward compensation scheme. Specifications achieved include high open loop gain (2200), low-power (15 mW or less depending on the load), fast settling time (0.1 percent settling time in 3 /spl mu/s for a 4 V input step and a 10 pF load), and small area. While this amplifier uses only a small number of transistors, its performance is comparable to that of recent depletion load amplifiers. Fewer critical steps are needed to fabricate this amplifier, making it attractive for large analog/digital LSI circuits.