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Voltage Regulator

The need for regulation:

Why do we need a voltage regulator to supply +5v when a 6v battery should be close enough?

Logic chips generally require a very stable +5v supply. The high speed CMOS family 74HC requires a supply between 2V minimum and 5.5V absolute maximum. Running this at 6v is likely to damage the ICs. Secondly, the regulator is able to respond to small fluctuations in the input voltage caused by other loads off the same battery switching on and off. It guarantees a +5v output signal as long as its input is a certain voltage above 5v (called the drop-out voltage), and the load on it is not too high. Single chip voltage regulators are available with a range of output current capabilities, from 100mA up to 5A and higher. For our purposes, using 74HC logic at relatively low frequencies, a 1 Amp regulator should be easily sufficient.


The regulator consists of a series pass transistor, and a feedback control circuit. It continuously monitors its output voltage, and compares it with a fixed voltage reference (+5V in this case). If the output voltage rises as the load current falls, it turns the pass transistor off slightly more. As more current is drawn, the voltage at the output of the regulator will start to drop, and the regulator will turn its pass transistor on slightly more to keep it up to +5v.

The capacitor between the battery and the regulator is required to ensure there are no high frequency variations in the supply to the regulator. The capacitor after the regulator is required to supply high frequency variations in the current drawn by the logic chips, which the regulator is not fast enough to react to.




Circuit Diagram: 

The above circuit Diagram gives the regulated power supply in various ranges starting from +5v to +12v.

These supplies can be used for various purposes such as Vcc for integrated circuits, supply for IR Led, and wherever constant power supply is required.















  1. mozahid
    September 17, 2008 at 8:37 am

    hi!how r u? i m a Bangladeshi.i m also reading Electronics and communication engineering.i want to know about electronics.i want to create myself new electronics cicuits.can u helf me.please how i can improve my practical knowledge.please tell me.

  2. September 22, 2008 at 7:58 am

    hi mozahid
    for knowing more about circuits and making them u first need to clear ur basics bout resistor, capacitor, diode, transistor, and inductor atleast. u can clear these from ur syllabus course or else from searching on net which i think is rather more advisable. then what u need to do is to search for projects on net, starting wid simple projects and then making them using breadboard by making little changes and then observing the difference using multimeter. also a visit to a small electronic industry is advisable.

  3. joe
    May 5, 2011 at 11:58 am

    You can call you’re local power company… Most of them have an HVAC training center which gives classes on things like basic electronics; transisters, capacitors, etc. And, the internet is most useful.

  1. May 21, 2008 at 6:26 am

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