The article explains the main specifications, datasheet and application notes of the IC LM123 which is a 5V, 3 amp fixed voltage regulator IC.


We have learned a lot regarding the IC7805 which is also a 5V fixed voltage regulator having excellent line and load regulation attributes.

However these are specified to produce a maximum of 1 Amp output, and therefore become less useful for higher current applications.

The IC LM123 includes all the impressive features of its above smaller counterpart and yet is enhanced for handling up to 3 Amps of load current.

The main features and specifications of this 5V, 3 Amp fixed voltage regulator can be studied from the following discussion:

Main Technical Features

  • Guaranteed 1% Initial Accuracy

  • Guaranteed 3 Amp Output Current

  • Built-in Current and Thermal Limiting

  • 0.01Ω Typical Output Impedance

  • Not more than 30W Power Dissipation

  • P+ Product Enhancement tested

  • No external component required for acquiring the rated 5V output

  • Is Virtually Blow-out proof

  • Package: Steel TO-3

Pin Out Details:

LM123 Electrical Specifications

The following parameters indicate the main operating specs of the IC LM123:

  • Input Voltage: Minimum 7.5V, Maximum 15V

  • Output Voltage: Minimum 4.7V Maximum 5.3V

  • Line Regulation: Typically 5mV at 7.5V and 25mV at 15V

  • Load Regulation: Typically 25mV at 7.5V and 100mV at 15V

Circuit Diagram of IC LM123, input 7.5V to 15V, output fixed 5V, 3Amp

Application Note:
Making a Solar Cell Phone Charger Circuit Using IC LM123

The following circuit shows one typical example where the above IC is effectively used for charging 3 to 4 cell phones simultaneously from a 12V 3 amp source. The source can be a lead acid battery, a AC/DC adapter or a renewable input such as from a solar panel, wind turbine etc.

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