The circuit shown in the figure is suggested by National Semiconductor and is based on an increased power transistor, which is the LM195. This transistor can provide a maximum output current of 1 A and consists of a Darlington with additional elements. The base excitation current is only 3 µA and it has a switching time of 500 ns with a saturation voltage of 2 V. The base can be excited by voltages of 40 V, without problems. In this application we have an RC power oscillator that operates at a frequency of 1 MHz. The housing of the LM195 is TO-3, and a TO-220 equivalent is the LM395T.
