This simple neon lamp oscillator produces a 140 Hz, 40 V peak-to-peak signal. The frequency is given by the capacitor that can have its value changed. Note the high supply voltage.
The circuit presented emulates an OR gate with the LM3900, operational transconductance amplifier....
This circuit was obtained from a 1962 magazine. It can still be mounted to be powered from 6 V...
The figure shows how to implement a conventional current monitor with differential amplifier on an H...