Many Electronic circuit projects in simple ways of learning

LM317 voltage regulator: Pinout, CALCULATOR and circuits

In the event we need to build a variable DC power supply that output of 1A and can adjust up to about 30V.
Most people will use LM317 because of high-efficiency, easy to apply and cheaper


It has an adjustable 3-terminal positive voltage regulator designed to supply more than 1.5 A of load current with an output voltage adjustable over a 1.2V to 37V range.

It has an internal current limiting, temperature detects shutdown and safe area compensation.

LM317 pinout

LM317 Pinout on TO-220

Figure 1: LM317 pinout on TO-220


LM317 pinout
Connection Diagram various LM317 Pinout

LM317T on TO-220: output 1.5A
LM317L on TO-92: output 100mA
LM317K on TO-3: output 1.5A
LM317 on DPARK: output 1.5A

-Output current in excess of 1.5A
-Output-Adjustable between 1.2V and 37V
-Internal Short-Circuit Current Limiting or Output is short-circuit protected
-Internal Thermal Overload Protection or Current limit constant with temperature
-Output-Transistor Safe Operating Area Compensation
-TO-220 Package like 2SC1061 transistors.
-There are 1% output voltage Durability
-There are max. 0.01%/V line regulation(LM317), and 0.3% load regulation (LM117)
-There are 80 dB ripple rejection
typical application of LM317
Figure 2 the basic circuit diagram

Basic circuit diagram
If power supply filter has distance from IC-regulator too much, should insert Ci to lower noise before IC-input. Next in figure circuit, Co is not needs if you do not high-efficiency, but we put it better, it is use for lower a output ripple.

As Iadj is controlled to less than 100uA, the little error Unimportant in most applications.

The input voltage to the LM317 must be at least 1.5v greater than the output voltage.

LM317 calculator

This calculator will work for most DC Voltage Regulators with a reference voltage (VREF) of 1.25. Typically, the program resistor (R1) is 240 ohms for the LM117, LM317, LM138, and LM150.

LM317 heat sink calculator

What is the size of heat sink enough?

While The LM317 is running. It is so hot. Though it has over temperature cut-out. But we do not need it hot. We always install the heat sink.

Someone ask me. How much should you use the smallest heat sink? LM317 has a maximum temperature of 50 °C/W  without a heat sink.

I found this site it good with LM317 heat sink calculator.

LM317 Heat sink, how big?

For example LM317 circuit

  1. Variable DC Power Supply 1.2V to 30V 1AFirst projects
  2. Linear power supply Regulator selector 1.5V,3V,4.5V,5V,6V,9V at 1.5A It’s easy to selects voltage output.
  3. 0-60 volt 30V Dual DC variable power supply using LM317 LM337 It’s high volt and start voltage at zero! good job.
  4. Best DC power supply 3Amp to adjust 1.2V-20V & 3V-6V-9V-12VHigh quality, 3A adjustable voltage regulator. Using LM317 and 2N3055 so easy and cheap. Adjust voltage in steps 3V, 6V, 9V, 12V. And In fine, 1.25V to 20V.
  5. 4 Lead Acid Battery charger circuits
    See 4 LM317 Lead-acid battery charger circuits for 6V, 12V, and 24V battery. With automatic charging and full charged Indicator using TL431. Easy to build.
  6. Dual power supply 3V,5V,6V,9V,12,15V
    Dual power supply circuit,can select voltage levels 3V,5V,6V,9V,12,15V at 1A and -3V,-5V,-6V,-9V,-12V,-15V at 1A, use LM317 (positive) LM337(negative) […]
  8. USB Battery Replacement
    This is a USB 5V to 1.5V Step-Down Converter Circuit. When we use a Cheap MP3 Player which use only one 1.5V AA battery as its power supply.
  9. Low dropout 5v regulator
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  10. Gel cell battery charger circuit
    It can charge any size of the Gel cell batteries and extend the life of the Gel Cell battery. While the circuit is running, the LED indicates charging.
  11. Nicad Battery Charger using LM317T
    Here is Universal nicd and nimh battery charger circuit. It use IC LM317T ( Hot IC) Control Current less 300mA, Size battery 2.4V,4.8V,9.6V. Low cost circuit

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This Post Has 6 Comments

  1. Thank’s & GBU this EC member .

  2. sir i want 5v,2a power supply circuit with calculation from 230

  3. pleasr can this idea be used to build solar charge controller?

  4. Pls suggest any simple circuit which supplies output of +12V , -12V dual output with current rating of 1A
    I/p supply is +24V DC .


  6. Dear Sir/Ma

    We are spare part supplier in Nigeria,
    Company name with address
    DE- ACCORD SYNERGY CONCEPT NIG LIMiTED. NO6, Oba Amusa Avenue Sumbol Bus Stop, Lagos Nigeria.

    Kindly quote us for the bellow items for our customer.

    LM78S40    (Universal Switching Regulator) 2nos

    LM7805      (Voltage Regulator) 2nos

    Your best price and delivery

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    Abiodun Ogundipe


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