# Super Steady Zener diode circuit

This circuit is used for controls the voltage battery is steady, which the zener diode apply very low current about 1mA only, cause there is ripple voltage about 1 mV at voltage changing between 10 to 30 volts. As circuit the output is fixed to 8V.

In circuit the reference voltage is connected to input of 741 OP-AMP (popular ICs) , to a non-inverting input and output of circuit will same the zener voltage multiply with OP-AMP gain as below.

Vo = Vz * {(R2 + R3)/R3}

The advantages of this circuit have two reasons.
(1.) we can use Zener diode that low temperature coefficient (5.6V), to cause the output voltage depend on the op-amp gain only.
(2.) the op-amp input not pull current from the zener diode. Thus the zener diode current is steady, then the resistor current is also steady. We so have the output as the really DC voltage regulator. And feedback to zener diode again by R1, current of zener equal (Vo-Vz) / R1

Therefore: We have to select R1 in current size about 1 mA flow through the zener diode. And maximum current flow into the output about 15mA at reference voltage.

Caution easily one: The DC voltage supply to the circuit should has higher voltage than the output about 1 volts.