The monolithic F--ET input stage has low bias currents (20pA) which minimizes the offset voltages caused by the bias current and the large resistance normally associated with high voltage circuits. The 3580 series is packaged in a TO-3 package which will dissipate over 3W of power without a heat sink and 4.5W with a suitable heat sink. The input stage is protected against overvoltages and the output stage is protected against short-circuitsto-ground. A special thermal sensing circuit prevents damage to the amplifier