Use of two power sources in voltage regulator using zener diode

Discussion in 'Homework Help' started by The Engineer, Jan 19, 2015.

  1. The Engineer

    Thread Starter Member

    Sep 3, 2014
    I am currently designing a voltage regulator using a 5V zener diode.
    I am wondering why some people choose to use two power sources instead of one, what would be the benefits of this ?
    the circuit is being simulated on multisim.
    the two attachments uploaded are as follows :-
    the one with one power source is my circuit which I am looking to improve
    the one with two power sources is a friends circuit, I cannot understand why they have used two power sources.

    any help with this will be greatly appreciated !

    also any advice on possible modifications to the circuit would be great ! I get points for testing circuit in different ways so any advice will help :)
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
    If you design a fixed positive voltage regulator, then you can use a single supply.
  3. ScottWang


    Aug 23, 2012
    According to your circuit, a calculation as below:
    Vout_741 = 12V - (1.4V~1.8V) = 10.2V~10.6V
    Vout = Vout_741 - Vbe = (10.2V~10.6V) - 0.7V = 9.5V ~9.9V
    V(-)_741 = Vout /2 = 9.5V ~9.9V = 4.75V~4.95V
    So here you have the output voltage around 9.5V ~9.9V.
    Is the voltage what you want?
    The 2N2222A can't afford too much current, are you just care about the voltage?
  4. crutschow


    Mar 14, 2008
    The dual supplies are needed if the op amp won't operate properly with a 5.1V input and the minus supply node going to ground (but most will).

    What improvements are you looking for?
    What's the maximum output load current you want to provide?
    Last edited: Jan 19, 2015