# Super Steady Zener diode voltage regulator circuit

This is a voltage regulator using Zener diode and OP AMP. The circuit is used for controls the voltage battery is very steady.

Which this circuit applies a very low current to about 1mA only.

Thus there is ripple voltage about 1 mV at input voltage changing between 10 to 30 volts. As the circuit, the output is the fixed voltage of 8V.

## How it works

We often use the Zener diode to make fixed voltage regulator. Because it is so cheap and popular use. But It doesn’t is a very stable voltage regulator. As it has ripple too much and changing voltage when temperature change.

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

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

The advantages of this circuit have two reasons.

• We can use Zener diode that low-temperature coefficient (5.6V), to cause the output voltage depend on the op-amp gain only.
• 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 do have the output as the real DC voltage regulator. And feedback to Zener diode again by R1, the 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 the reference voltage.

Caution easily one: We use the DC voltage supply or unregulator to the circuit should have the higher voltage than the output about 1 volts.

#### Parts you will need

• IC1: LM741 – OP-AMP
• ZD1: 5.6V 0.5W Zener diode
• R1: 2.2K – 0.25W Resistor
• R2: 220K – 0.25W Resistor

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