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    This circuit regulates a DC power output. It has a very wide application range. It can be used to control the speed of a motor, a pump, a toy train, the brightness of a LED or lamp, etc. Practically, it can be used in any application that uses a regulated DC power with pulse width modulation (PWM).
    It was originally used as a jumbo LED dimmer.

    The circuit works this way: the A1 opamp functions as a square wave generator. At its non-inverting input is a by product triangle wave signal. The IC A2 following it functions as a simple comparator. A reference voltage is fed to the inverting input of the A2 IC via the potentiometer P1. The output of A2 is a square wave signal with a constant frequency of around 200 Hertz.
    This signal has a variable pulse width from 0 to 100%.

    DC regulator circuit diagram

    dc regulator circuit schematic

    The P1 sets the trigger point of the pulse. The transistor T1 works as the actual regulator by switching a relatively high current with a maximum of 5 amperes. The power supply voltage must be between 5 volts (minimum) and 30 volts (maximum). Take note that the lower the supply voltage is, the lower the efficiency of the dc regulator becomes.

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    11 Responses to "DC Voltage Regulator Circuit"

    1. what’s for is c2? i’m a newbie and please reply…

    2. C2 is simply a power supply decoupling capacitor that reduces noise etc. It does not need to be this large. 10uF is OK.

      What is not shown is how to connect the op amp power terminals–refer to device spec sheet for this detail.

      To drive an inductive load (e.g. motor), add a rectifier across the output terminals with the cathode connected to “+” and the anode connected to “-“. Otherwise, T1 is subject to failure.

    3. peterf@dyechem.co.za says: on May 3, 2013 at 1:57 pm

      How do I get the spec sheet for the DC voltage regulator circuit?

    4. Hi
      I would like to build a DC-DC converter with 6v Dc input and 4-60 volt dc adjustable output the outpt current is 30ma.

    5. what can i used besides 2N6666

    6. Very hard bt easy that manufacturing to make the circuits.i can’t explai how much i learn from this.

    7. This circuit is simple, cost effective and useful for low cost regulation system.

    8. Ramesh Keshav Phadke says: on September 19, 2015 at 1:53 am

      Dear sir.

      Thanks for sending these circuits I have been waiting for


    9. how much will be the output regulated voltage if the input voltage varies between 4 to 6v?

    10. What is the schematic of the ca3240. And where can I get on for cheep

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