This variable filter circuit was found in July 1975 Radio Electronics magazine. The circuit uses 3 general purpose op-amps like the 741 and must use a symmetrical source.
The indicated circuit performs a slow charge of 12 V batteries maintaining a constant current of...
Found in a 73 magazine from the 1980s, this circuit generates signals from 3.2 to 22 MHz. FETs can be...
In the figure we have a three-phase AC motor control for voltages up to 600 V or 1200 V depending on...