A monolithic junction FET-n-p-n operational amplifier

A monolithic operational amplifier with junction FET inputs in combination with n-p-n bipolar transistors is described. Both dc and small signal analysis of the amplifier are carried out. Electrically the devices are comparable with discrete state-of-the- art p-channel FET's. The circuits are fabricated with a process requiring a single diffusion more than standard techniques. The process is reproducible enough to allow economical fabrication. The amplifier realizes input currents of less than 1 nA, a minimum slewing rate at unity gain of 75 V//spl mu/s and bandwidths in excess of that of any monolithic operational amplifier reported to date.