How to build a +5V regulator using 78L05 / 7805

This is a very simple article, just trying to help ….
What is the most vital piece we always need in electronics? The answer is …. a good power supply, right? 😀 .
The best regulators for using in electronic projects are the 78LXX (78L05, 78L09, 78L12, 78L15 … ). I searched google for the application notes and I found them easily (look in the bottom part of the page for the download link).
Their typical application was the IC + 2 small condensers (the input is at 0.33uF and the output is at 0.01uF), but after some tryouts and more googling I found this page which, too be honest with you, I consider it to be the best circuit over the web.
I tested the circuit and it worked like charmed.
Reading the application note we see that the input voltage must be between 7V and 20V and the output voltage is between 4.75V – 5.25V .



  • IC1 = 78L05 / 7805
  • D1 = 1N4007
  • C1 = 100uF
  • C2 = 10uF

Bibliography :

The 78L05 Datasheet :

53 comments on “How to build a +5V regulator using 78L05 / 7805

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  3. Hi,
    To what pin of the computer(i.e in the DB25 connector) do we need to connect the input of this voltage connector ?

  4. hey sorin,
    i need a similar circuit for my project but i want the input voltage to be max 6 volts coz my device will have to run on a battery.
    plz reply as fast as possible


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  7. Hey Sorin,

    Your power supply circuit works perfectly.Thanks a lot! I’m not a professional…so please dont mind if my questions sound a bit silly. Can you explain what exactly are the functions of the two capacitors connected at the input and output? If we dont use the caps, there seems to be drop in source voltage. Why is that?

  8. Is it possible to use a LM7805CT to drive it? and what capacitance should i use for C1 and C2 if LM7805CT can be used?

  9. Hey,

    I’ll start by saying I’m new to this.
    I was trying to build my first power regulator circuit, followed a diagram and all seemed fine.

    When testing, connected to a 9v battery (9,5v brand new) the circuit output was 8,9v representing a 0,6 v diference.
    I checked all the circuit, replaced capacitors and the 78L05 as well just to be sure. Got the same result.
    Lowering the input to 7,5v the power output had 6,9 wich represents the same 0,6v in diference.
    After this I even tested it alone with no capacitors and got the same result.
    What is happening here? Am I so unlucky I got two malfuncioning power regulators?
    Is there any other possible explanation?

    Thanks for any help.

  10. Thanks Sorin,

    That was it. Incredibly I did download a similar document and had a very good look at it until I was sure to be getting it right. It’s obvious I didn’t. So many trys and never swiched it because I was so sure to be doing it right. No heat for me meant everything fine. Only now I understand that it heats when you invert its polarity that is completely diferent. Thank you very much for even replying to a dum question like this but it really helped.

    Best regards,

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  13. Hey is there any way to calculate +5V regulator using 78L05 / 7805 circuit (the above circuit) please?

  14. sir i want to make a regulated powersupply using 5regulator e.g 7805 ,7809,7812,and also 2regulator which give me -ve supply . please help me out.

  15. Hi, this is my 1st post here. An interesting alternative to this classic IC is the MC34063
    switching IC which is commonly used in cellphone car chargers. It is pretty effecient and simple to use, and you can usually use the PCB as is. It is also voltage adjustable and there is a very handy design tool available at The IC is dicontinued from major suppliers, but easy to find at thrift stores. Usually, as supplied in chargers, it’s good for about half an amp, but can supply much more with a power transistor and a 5 to 25 uH choke. Datasheets are on the web. Oh, use a switching frequency between 30kHz & 180kHz – higher is better.

  16. Hello I’m new in the circuits field and I’m building a room temperature regulating system…. Is it are there non multi-pin And and Not gates????

  17. hello sir please give me the complete circuit design of full wave centre tapped rectifier which ll give output as 5v dc please reply soon sir i need it urgently

  18. Stefan,
    The 78L05 is rated to output up to 100 mA. The 7805 is rated 1 Ampere. By the way, the power which the regulator must dissipate as heat is equal to (input voltage-5)*current.
    If you put 9 volts in, and pull 1 ampere, this means 4 Watts are produced as heat! You may need to use a heat sink, depending upon your application. Check to see if the regulator gets hot.

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  20. hey,,…can any body tell me..why we are using capacitors and how their
    values are selected

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  22. For only $9 you can buy on ebay a voltage, amperage regulator. With two linear trim pots you can adjust the voltage from 1.2V to 15V, and the current from 150mA to 5 A, with increments 0.1 units. You need to buy a DC power supply. American Science Surpluss sells a bunch of them, 4V to 12V with current 500mA to 1000mA for less then $4, if you do not want to waste your time to find a transformer core calculate mgnetic permiability, find copper wires for primary and secondary, build it, add diodes capacitors, inductors i.e. Invent the wheel.

  23. Thx for the schematic. It does work like a charm. Not only did I build it I am using this circuit along with a salvaged USB port from an old desktop and using it as an emergency battery operated cell phone charger.

  24. nice work here…. I build the same circuit.. taking my source from a 10.35V solar panel, I got a 5.02V output when read with my multi meter but it drop once I plug in my mobile phone USB or add an LED at the output… could dis be as a result of my capacitors which has voltage rating of 16V?

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