LM723 Voltage Regulator Working and Its Applications

There are various types of voltage regulators for getting a regulated power supply like 7812, 7805, etc. However, all these regulators provide a fixed value output. For inconsistent voltage regulation, an LM317 IC voltage regulator is used which we have discussed in the previous article. At present we are designing an LM723 based voltage regulation circuit, and this is the most famous integrated circuit in voltage regulation. This circuit can be built with the basic electronic components like IC, resistors, and capacitors. For example, if we use 9V supply to this circuit, then the regulated supply can be adjusted from 4volts to 8volts with the help of a potentiometer. The main purpose of using this IC is to provide an extreme amount of current by using an exterior pass transistor. Here the range of the extreme amount of current will be up to 10A.

About LM723?

LM723 IC is a changeable voltage regulator, used in the series regulator application with 150mA current o/p without exterior pass transistor. When we utilize an external transistor, then it supplies 10A current to drive the load. The input voltage supply is maximum 40V & its o/p voltage ranges from 3volts to 40volts.


The applications of this IC mainly include current regulator as well as a shunt regulator. This IC includes low supply current drains that will allow using this IC like folding back current limiting, linear with the range of operating temperature -55 °C to 150 °C. The equivalent voltage regulators of the LM723 IC mainly include MC1723CP, LM723CN, LM723N, LM723QML, and LM723CMX

LM723 Pin Configuration

The Pin Configuration of the LM723 and each pin is discussed below.

LM723 Pin Diagram
LM723 Pin Diagram
  • Pin1 (NC): Not connected
  • Pin2 (Current Limit): This pin is used to limit the current
  • Pin3 (Current Sense): This pin is used in foldback application as well as to limit the current
  • Pin4 (Inverting Input): This pin provides stable o/p voltage
  • Pin5 (Non-inverting Input): This pin is used to supply a reference voltage to the inside of the operational amplifier.
  • Pin6 (Vref): This pin provides an almost 7v reference voltage
  • Pin7 (-Vcc): GND (Ground) Pin
  • Pin8 (NC): Not connected
  • Pin9 (Vz): This pin is generally used to make negative regulators
  • Pin10 (Vout): This is the o/p pin
  • Pin11 (Vc): This is the series pass transistor’s collector input. Generally, it is connected directly to the +ve voltage supply if an exterior transistor is not used.
  • Pin 12 (V+): This is the input of the positive supply
  • Pin13 (Frequency Compensation): This pin assists in decreasing noise with a 100pf capacitor
  • Pin 14 (NC): Not connected.

LM723 Features

The features of the LM723 include the following.

  • The unnecessary o/p current will be 150mA without using an exterior pass transistor.
  • The maximum input supply voltage will be 40V.
  • It offers modifiable o/p from 3volts to 37volts.
  • These ICs are used to make switching & linear regulator.
  • It supplies 10A o/p current with the help of an external pass transistor.
  • These ICs are used for different operations such as positive, negative, series, floating, and shunt.

LM723 Specifications

The specifications of the LM723 include the following.

  • The maximum i/p voltage is 40v
  • The reference voltage is always 7 volts
  • Ripple rejection is 74 dB
  • The current supply from Vz pin is 25mA
  • The output voltage ranges from 3volts to 37 volts
  • The range of operating temperature will be from -55°C to +150°C
  • The current supply from Vref pin is 15mA
  • The line and load regulation of 0.01%Vout & 0.03% Vout

LM723 Internal Block Diagram

The internal block diagram of the LM723 IC is shown below. This block diagram can be explained by separating it into two blocks namely the error amplifier and the reference voltage generator.

In the reference block, a Zener diode is being forced to work at set point, so the o/p of the more zen is a permanent voltage with a stable current supply which arrives to produce a stable voltage (7.15V) along with an amplifier on the Vref pin of the IC.

LM723 Internal Block Diagram
LM723 Internal Block Diagram

In the error amplifier block, it includes a series pass Q1 transistor, an error amplifier, & a transistor which limits the current. This amplifier is used to contrast the o/p voltage which is given at inverting i/p terminal throughout feedback toward the Vref-reference voltage given at the non-inverting terminal.

The two connections internally not offered & so have to be externally offered in accordance with the required output voltage. The conduction of the transistor Q1 is controlled by the error signal. It is this transistor that controls the output voltage.

Advantages of LM723 Voltage Regulator

The advantages of LM723 voltage regulator include proven, low noise, the voltage range is wide, support for external pass transistors, recompense by the user, extremely flexible, complete temperature range accessible, and economical

Disadvantages of LM723 Voltage Regulator

The disadvantages of LM723 voltage regulator include difficulty, current limiting is not exact, current limiting is sensitive to overload, lowest dropout voltage, least regulated o/p voltage, error amplifier gain is Moderate, error amp bias current, and be careful when using MOSFET pass transistors.

Thus, this is all about the LM723 IC datasheet. It is an adjustable voltage regulator and the applications of LM723 mainly include a temperature controller, shunt and current regulator. It provides a high range of o/p voltage & current equal to 10A by just inserting a sequence pass transistor through it, by including an extensive range of working temperature. Thus the integrated circuit capable to withstand for long to use like linear otherwise switching kind regulator. However, this integrated circuit is particularly designed for series regulator function. Here is a question for you, what is the main function of LM723IC?