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.
The circuit is from Motorola's Linear Databook from 1990, but the configuration is current because...
In the figure we have the simplest way to implement a power supply for a tunnel diode. The...
This circuit was found in documentation from the 1980s. The circuit can be implemented with other...