Found in a 1967 publication by General Electric, this control is intended for motors up to 2 A according to the SCR used. Higher current equivalent SCRs can be used.
The circuit shown in figure 5 generates square signals based on a transconductance operational amplifier...
By adding a transistor to the output and some polarization features we can obtain a higher output...
Found in the 1990 special issue of Radio Electronics Experimenter magazine, this circuit uses an...