This circuit is suggested by the National semiconductor and is based on an increased power transistor which is the LM195. The circuit is shown in the figure. This transistor has a maximum output current of 1 A and consists of a Darlington with several support circuits that can be excited with a base current of only 3 uA. The transistor in question has a switching time of 500 ns and a voltage of 2.0 V saturation. Its base can be excited by voltages of up to 40 volts without problems. In this application we have an RC oscillator. The transistor housing is TO-3, but there is an equivalent in TO-220 housing which is the LM395T. In both cases, the transistor must be mounted on a heat radiator.
