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.
This circuit is from a 1967 publication. It is possible to power a fluorescent lamp from a 12 V...
This circuit was found in old American documentation. Transistor is general purpose and coil rated...
With a strong positive feedback (via a 10 M resistor) we can get the trigger setting for the...