This circuit with the HA2400 was found in the March 1980 Radio Electronics magazine. The circuit has digital-gain control and must be powered by a symmetrical 15 V source.
Suggested by an American documentation for 1969 neon lamps, this circuit provides SCR control with...
This circuit is designed to measure very weak currents, in the order of picoamperes. We found it...
The 709 integrated circuit is not common today. The circuit is from American technical...