Found in a documentation for radio amateurs from the 90s, this circuit is suitable for RF measurements in transmission systems. The potentiometer must be of a special type.
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....