The minimum and maximum power supply voltage for the "diode" depends on the operating voltage of the operational amplifier. At higher voltage, you can lower the power to the amplifier with a stabilizer on a small zener diode. With a lower voltage, you need to look for a lower voltage amplifier. Personally, I used 4558. The motor on the right is a fan used to cool the radiator of this "diode", it turns on only when it is working. The resistor that supplies it (here 100ohm) should be selected according to the power and voltage of your fan.
