Self Oscillating Converter(Transistorised Chopper Circuit):
A Self Oscillating Converter(Transistorised Chopper Circuit) dc to ac converter suitable for low level dc signal is illustrated in Fig. 14.30.
The unique property of this assembly is that it starts to oscillate vigorously at very low levels of dc collector voltages at only a few micro-watts of collector power. The circuit shown in Fig. 14.30, is connected in a tickler feedback, common emitter configuration. Referring to Fig. 14.31, the centre tapped transformer provides the output for the ac amplifier.
The dc gain can be varied, within limits, by the 100 k potentiometer connected in the collector circuit. The AF oscillator is completely inoperative, unless an input signal is applied to it. The polarity must be reversed for a PNP transistor. Rectification of the ac output may be done with the simple full wave rectifier circuit. This circuit connected to the amplifier output secondary transformer is shown in Fig. 14.31.