This is the typical circuit of a local oscillator for a superheterodyne FM receiver. The circuit was found in a 1980s documentation and is typical of early and early receivers.
This circuit uses a FET to drive an LED with constante currente. The current up to 20 mA can be...
The TDA2040 is not a common IC these days, but if you find one you can build this high quality...
This ouput push-pull stage using bipolar transistors was found in a publication of the year 1968....