Voltage Regulator | Circuit Diagrams | 8+ Different Types | Important Applications


  • What is a Voltage regulator
  • Types of a voltage regulator
  • Voltage regulator Circuit
  • Zener Diode as a voltage regulator
  • Difference between series regulator & shunt regulator
  • Series regulator
  • Shunt regulator
  • Regulated power supply
  • The function of the voltage regulator
  • Percentage regulation
  • Applications of a voltage regulator

What is the voltage regulator?

Definition of voltage regulator:

A voltage regulator is a DC regulator that offers a constant DC output voltage that is fundamentally independent of applied input voltage, output load current, and temperature.”

Also, the regulator output can be changed as per the requirement. Hence, the function of a voltage regulator is two-fold 1. The output voltage can be regulated at the desired level. 2. The regulated voltage at the output can be maintained constant despite disturbances in supply voltage or change in load.

Types of a Voltage Regulator:

Classifications of Voltage Regulator:

  • The Zener Diode Based Shunt Regulators
  • The Transistor Based Shunt Regulators
  • The Transistor Series Regulators
  • The Transistor Current Regulators
  • The Transistor Controlled Series Regulators
  • The Op-amp based Shunt Regulators
  • The Op-amp based Series Regulators
  • The Switching Voltage Integrated Circuit Regulators
  • The Monolithic Regulators

Voltage Regulator Circuit:

The following figure refer to the Zener diode of a regulator.

Voltage Regulator Circuit, Image Credit – anonymous, Simple electromechanical voltage regulatorCC BY-SA 2.5

The input current, IS=VS-VZ/RS

Where VS= d.c input voltage to the regulator circuit VZ= Zener voltage

The voltage across Zener diode terminals,

VL=VZ + IZ rz

VL=VZ (Itrz is negligible)


Input current, IS=IZ + IL or IZ= IS – IL

Zener Diode as Voltage Regulator:

Zener Diode as Voltage Regulator Image Credit – I, AppaloosaVoltage stabiliser transistor, IEC symbolsCC BY-SA 3.0

In this circuit, a Zener diode is joined in reverse biased parallel with a variable voltage source supply. The Zener diode in this circuit will operate when the voltage at the reverse breakdown voltage. Then, the diode’s relatively low impedance retains the voltage.

This is a typical voltage regulation circuit with an input voltage, VIN. This voltage is regulated down to a stable output voltage, namely VOUT. The breakdown diode voltage is stable over a wide current range and maintains VOUT at relatively constant even though the relative voltage may fluctuate during this operation.

As per Ohm’s law diode current, flowing through the diode, a load is placed across the diode, and as long as the Zener diode operates in a reverse breakdown, the diode will deliver a stable voltage to the load. Zener diodes in this stage are often used as a stable regulator for more advanced circuitry.

Series Regulator Circuit:

The basic block diagram of the series regulator circuit is shown below. The control element is connected in series with the load in between i/p and o/p terminal. The sampling circuit detects the variation in the output voltage. The comparator circuit will compare sample voltage with a reference one. The control element will compensate during that period and will retain a constant output. The control element conducts more when V0 reduces and conducts less when V0 increases.

Series Voltage Regulator

Here a simple series regulator is presented. Transistor Q is the controlling element that is in series. The Zener diode provides the reference voltage.

Regulator with op-amp, Image Credit – I, AppaloosaVoltage stabiliser OA, IEC symbolsCC BY-SA 3.0

Shunt Regulator Circuit:

In the linear voltage regulator category, in the shunt regulator circuit, the output is monitored, and the feedback signal initiates changes in input signals to maintain the desired output. However, in series regulators, the control unit or regulating unit is in series, and in shunt regulators, the control unit is in the shunt. The basic block diagram is shown below,

Shunt Voltage Regulator

In the case of shunt regulators, as the control element is in shunt, it conducts more to provide regulation by shunting current away from the load.

What is Regulated Power Supply?

A regulated power supply is a stand-alone unit. It is able to supply a stable voltage to a circuit. This has to be operated within specific power supply limits. The regulated power supply output might be alternating or unidirectional but it is nearly a DC in standard operation.

The type of stabilization be limited to confirm that the output remains within absolute limits under a number of load condition.

The specification parameters are:

  • The Input Voltage parameter
  • The Output Voltage parameter
  • The Output Current parameter
  • Stability factor
  • Ripple factor
  • The Stored Energy
  • The Pulsed operations
  • The Load Regulation
  • The Line regulation
  • The Dynamic Regulation
  • The Efficiency.

Comparison between Shunt and Series Regulator

ParameterShunt Voltage  RegulatorSeries Voltage Regulator
ConnectionIt is connected in parallel with loadIt is connected in series with load
Load CurrentAt high load current, has good voltage regulation.At high load current, does not have an effective voltage regulation.
OutputConstant DC Output voltage.Varying Output voltage.
Control ElementHigh voltage low current circuitryHigh current low voltage circuitry.
SuitabilityIt is good for light loadsIt is good for heavy loads.
EfficiencyGood efficiency for low load current.Good efficiency for heavy load current.

What is the function of a Voltage Regulator?

A voltage regulator is to provide a constant DC output which is independent of the input voltage, output load current, and the temperature. It is an important component of a power supply circuitry. Its input voltage supplied from the rectifier circuit. The low capacity (500VA) regulators are in general used for domestic applications, for television, refrigerator, air-conditioner, etc. and for necessary equipment like computers. In these medical instruments, the sudden changes in voltages can affect the equipment leading to erroneous results and may get damaged ultimately.

What is the Percentage Regulation?

The basic performance measures for a regulator are line regulation and load regulation parameter. The line regulation is defined as the change in percentage of the output voltage for a given change in the input voltage as explains follows:

Uses of Voltage Regulators:

  • Voltage Regulators is used in low output voltage switching power supply circuits.
  • It is used in error amplifiers design.
  • In design of the current source and  the sink circuits
  • These are used for voltage monitoring and maintenances.
  • It is used to design the Precision current limiter circuitry. It is applied in Analog and Digital Circuits for precision reference.
  • It is used in adjustable voltage or current linear circuitry etc.

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About Soumali Bhattacharya

I am currently invested in the field of Electronics and communication.
My articles are focused towards the major areas of core electronics in a very simple yet informative approach.
I am a vivid learner and try to keep myself updated with all latest technologies in the field of Electronics domains.

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