Voltage Regulator

Discussion in 'General Electronics Chat' started by artmaster547, Jan 19, 2016.

  1. artmaster547

    Thread Starter Member

    Jan 6, 2016
    89
    1
    Hi all

    I am trying to create a regulator I have a supply that is 9V but can vary between 12 and 6, I have attempted something below but it's not functioning in the way I intend any guidance or alternatives would be really appreciated. I want the regulator to output 9V or something close to this as long as it's consistent at the output with the range of inputs 6v-12v.
    Thanks
    Art
     
  2. artmaster547

    Thread Starter Member

    Jan 6, 2016
    89
    1
    Sorry I would like to make an amendment not 9v I meant 4 volts apologies about this
     
  3. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    632
    If you want the regulator to output 9V then you will have to supply its input with more than 9 volts. Generally, you will need 11 or 12 volts input for this circuit.

    Also: You will have to adjust the feedback divider to get 9 volts out assuming 6.9 volts on the base of Q1. The ratio will not be exact because of base current into Q1, and

    You will probably have to decrease R1 to get enough current (figure 5 to 10 ma) into D1 to get its voltage close to 6.2 volts.
     
  4. dannyf

    Well-Known Member

    Sep 13, 2015
    1,771
    358
    Your zener is of the wrong voltage.

    Simpler approach is to use a 3 terminal regulator.
     
  5. DickCappels

    Moderator

    Aug 21, 2008
    2,647
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    Post-amendment comment (now that we know you want 4 volts out).

    Change D1 to a 3.3 volt Zener (make sure you run enough current to get 3.3 volts), and omit R3. You can also replace R4 with a short. Vbe Q1 = about 0.6 volts, Vz D1 = about 3.3V, the sum being equal to 3.9 volts.
     
  6. artmaster547

    Thread Starter Member

    Jan 6, 2016
    89
    1
    Should I get rid of Q2 as well then?, or should that be the same as Q1, and to get D1 to 3.3V do I change the diode or the resistor that control the current flow

    Thanks Art
     
  7. artmaster547

    Thread Starter Member

    Jan 6, 2016
    89
    1
    Could you provide a drawing by any chance would really appreciate it thanks
    Art
     
  8. dannyf

    Well-Known Member

    Sep 13, 2015
    1,771
    358
    You can use a led in place of the zener, as 3.3v is still a little too high for what you want to do. And an led also functions as a power indicator.

    Or you can simply short the zener.
     
  9. artmaster547

    Thread Starter Member

    Jan 6, 2016
    89
    1
    Thank managed to get something working now thank you so much all of you for the help
     
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