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Simple Regulated Adjustable Power Supply Circuit using IC 723

This post shows you how to build a special power supply circuit that can adjust the voltage it gives out.

It uses a special chip called a LM723 sometimes called an IC 723.

This chip is great because it can take a changing voltage from your power outlet and make it steady, and you can also turn a knob to adjust how much voltage power it gives out.

This is useful for powering many electronics projects.

Circuit Working:

Parts List:

ComponentQuantitySpecifications
Resistors
0.56Ω11W
750Ω11/4 watt
2.7k11/4 watt
Potentiometer
1k1
Capacitors
Ceramic 470pF1
Electrolytic 2200µF 25V1
Semiconductors
IC LM7231
Transistor
2N30551

The potentiometer serves the purpose of finely tuning or, modifying the internal reference level of the IC 723, ensuring a stable output from the IC as follows:

By gradually moving the slider arm of the potentiometer towards ground it influences the inverting pin of the op amp causing the output voltage to rise.

As the potentiometer slider is moved downward along its track instead of stabilizing the output at a voltage identical to the reference voltage the feedback loop adjusts the inverting input of the op amp to match the voltage developed by the potentiometer.

With a reduced potential across the potentiometer pins, the output voltage is prompted to increase aligning the inverting input to the appropriate voltage level.

Further movement of the pot center wiper arm downward results in a proportionally higher voltage drop, causing the output voltage from the IC to rise accordingly.

To illustrate this, suppose the pots center wiper is moved two thirds down.

This action might result in a feedback voltage to the op amps inverting pin being one third of the output voltage.

This mechanism stabilizes the output at a potential three times higher than the reference voltage ensuring the appropriate voltage level on the op amps inverting input.

Hence, this feedback control via a potentiometer facilitates adjustable output voltage with efficient stabilization.

Output Voltage Calculation using formula for a fixed constant stabilized output voltage the potentiometer can be replaced with a potential divider network using R1 and R2 resistors as depicted below:

Formula: 1 (R1 + R2) / R2

Volts determines the desired constant output voltage where R1 is connected between the output and the inverting input of the operational amplifier, and R2 is connected between the inverting input and the negative supply line of the device.

This arrangement links the reference voltage directly with the non inverting input of the IC 723 internal op amp.

The number 7 in the formula signifies the reference value and the minimum output voltage the IC can produce.

To obtain fixed output voltages lower than 7V this number can be substituted with the desired minimum voltage value in the formula.

However, the minimum output voltage for IC 723 cannot be less than 2V.

Thus, the formula for setting the output at 2V becomes:

Formula: 2 (R1 + R2 )/ R2

Understanding the Current Limiting Feature in IC 723:

The IC 723 provides precise adjustable current control at the output based on the load requirement.

A set of discretely calculated resistors are utilized for sensing and limiting current to desired levels.

The formula for determining the current limiting resistor is basic and is as follows:

Rsc = 0.66 / Maximum Current

How to Build:

To build Simple Regulated Adjustable Power Supply Circuit using IC 723 steps are mentioned below:

Prepare Components:

Connect IC 723:

Set up Voltage Divider:

Integrate Potentiometer:

Set Current Limiting Resistor:

Complete Op Amp Setup:

Power Supply:

Testing:

Adjustment:

Current Limit Testing:

Note:

Conclusion:

In conclusion, a regulated adjustable power supply circuit utilizing the IC 723 voltage regulator offers a compact and efficient solution for generating stable and adjustable DC voltages.

By incorporating feedback control and filtering components it ensures consistent output voltage levels despite fluctuations in input voltage or load.

With its versatility and reliability, this circuit finds widespread application in electronics from powering sensitive devices to serving as a fundamental component in laboratory equipment and audio systems.

References:

LM723/LM723C Voltage Regulator

Power supply with LM723

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