Found in a 90s 303 Circuits, this circuit triggers a load from a 50 mV audio signal. When the signal ceases, the charge remains active for 2 seconds.
This amplifier with very high input impedance was suggested by Texas Instruments in a manual of...
Using only a ULN5804 integrated circuit, stepper motors up to 500 mA can be controlled from TTL...
Constant current sources are used in applications such as battery chargers, electrolytic tanks, etc....