This 2-quadrant modulator circuit was found in the May 1988 issue of Radio Electronics magazine. The CA3080 is an OTA operational amplifier.
In the figure we have a typical detector stage for a radio receiver. The circuit is from 1963,...
Found in a 1968 Texas Instruments documentation this circuit uses an SCR from that time. Modern...
This circuit was obtained from an American publication of the 80's. The integrated circuit is of the...