Skip to main content

L4940V5 Low Dropout Regulator

The L4940V5 is a 5V low dropout voltage regulator from ST Microelectronics, with a low dropout voltage of 450mV at 1A load. It is suitable for battery-powered operation and helps prolong battery life. It comes in a TO-220 package and has internal current and power dissipation limiting.


L4940V5 Pinout Description

Pin Number

Pin Name




Input supply pin



IC ground reference



5V output pin


Features and Specifications

  • 5V output ±10mV
  • Low dropout voltage (450mV)
  • Thermal, overcurrent, and reverse voltage protection
  • Peak Output Current: 2.25A at 2V differential
  • Quiescent Current: 5mA


Note: Complete technical details can be found in the L4940V5 datasheet linked at the end of this page.


Equivalent for L4940V5


Other Voltage Regulators

LM7805, 78L05, LM317


How To Use L4940V5

The L4940V5 is a 5V low dropout voltage regulator. Most voltage regulators require that the input voltage is at least a few volts higher than the output voltage for proper regulation since the output is based on an NPN stage. In the case of a low dropout regulator, the output stage is PNP-based, meaning only the VBE drop is seen from the input to the output, so much lower dropout voltages can be achieved. This means that the regulator can operate even when the input voltage is a few hundred millivolts above the input. This is particularly useful for battery-powered instruments, otherwise, the high dropout voltage means that a lot of battery capacity is wasted.

An important thing to note is that low-dropout regulators can be unstable, so output decoupling has to be added carefully. No decoupling or decoupling with too little internal resistance can cause the regulator to oscillate.

L4940V5 Application Circuit



  • On-card regulation
  • Linear output stage for SMPS
  • Battery-powered electronics


2D Model and Dimensions

L4940V5 Regulator Dimensions

Component Datasheet

Related Post

Join 20K+subscribers

We will never spam you.

* indicates required

Be a part of our ever growing community.