This digital circuit is from a Radio Electronics magazine from December 1991. It does not use a microcontroller, but rather discrete digital circuits of the time.
In the figure we show yet another CMOS component based voltage controlled oscillator circuit. The...
This 80's circuit uses an operational amplifier of the time. The circuit can be applied to modern...
This circuit, which uses only common transistors, was obtained from a 1988 publication, but can be...