This small control for DC motors up to approximately 1 A uses an operational amplifier that admits equivalent. The transistor can be TIP29 for currents up to 1 A or BD135 for 500 mA.
Found in General Electric and 1967 documentation, this circuit automatically turns off the...
This amplifier stage without an output transformer was found in Radio Electronics magazine from...
Found in an Electronics World of 1968 this circuit can use current SCRs and the diodes are...