This amplifier with fixed AC bias was found in a 1947 documentation. The circuit uses two transformers in the power supply and two full-wave rectifier tubes.
We adapt this circuit of Radio Electronics - March 1990. The magazine no more exists, but the...
This circuit is a digitally controlled variable capacitor. We found it in American documentation from...
In the circuit shown in the figure, when the input voltage rises to 27 V, the TL431 triggers the...