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2 volt regulator

Discussion in 'General Electronics Discussion' started by Nick Lee, Apr 28, 2018.

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  1. Nick Lee

    Nick Lee

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    Mar 4, 2018
    Is there a chip like a lm78_ _ that will regulate down to 2 volts?
     
  2. Chemelec

    Chemelec

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    Jul 12, 2016
    I have a Few MC7902CT Regulators .
    these are 2 Volt Negative regulators.
    Probably the 2 volt Positive ones Were also Made.
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Do you mean regulators that will produce an output of 2 volts, work with a differential voltage of 2 volts, or work with an input voltage of 2 volts?
     
  4. AnalogKid

    AnalogKid

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    Jun 10, 2015
    Probably not. -2 V is the termination voltage for ECL. There was no equivalent regulated positive voltage needed for other logic families or linear components.

    For a single isolated output, the 7902 can be used to "regulate the ground" and produce a +2 V output, but that technique will not work if the +2 V output has to have a ground that is common with other positive output voltages.

    ak
     
    Last edited: Apr 28, 2018
  5. Chemelec

    Chemelec

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    Jul 12, 2016
    Depending on his situation, this Negative one could work for him.
     
  6. Chemelec

    Chemelec

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    Jul 12, 2016
    An LM317 will also Regulate down to 2 Volts or a bit Lower.
     
  7. kellys_eye

    kellys_eye

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    Jun 25, 2010
    What's the application? There are a load of 1.8V regulators for modern processors and this might be within any tolerance the user requires???
     
  8. Audioguru

    Audioguru

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    Sep 24, 2016
    I think he is trying to burn out a red LED.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    So, are you guessing, or do you have other information that you're deliberately withholding?

    Either way... not very helpful.
     
  10. Audioguru

    Audioguru

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    Sep 24, 2016
    He made only one post without saying what the 2V is for or how much current he needs. He did not say if an LM317 can be used.
     
  11. Nick Lee

    Nick Lee

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    Mar 4, 2018
    No Audio is almost correct, i have am trying to step down a voltage of about ~17 to about 2 for some white LEDs .
     
  12. AnalogKid

    AnalogKid

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    Jun 10, 2015
    Most LEDs - and particularly white LEDs - should be driven with a specified current, not a regulated voltage.

    Part number / manufacturer / specs?

    ak
     
  13. Audioguru

    Audioguru

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    Sep 24, 2016
    It sounds like you did not measure the voltage of a white LED. It is much more than 2V, probably between 2.8V and 3.5V. You said LEDs in plural. If you connect a bunch of white LEDs in parallel then since they all have different voltages, the LED with the lowest voltage will take all the current and quickly burn out, followed by the LED with the next low voltage and it will burn out, followed by ... etc. The voltage of an LED drops as it gets warm which makes it draw more current which makes it warmer which makes it draw more current which makes it... have thermal runaway and it goes POOF!

    Buy thousands of white LEDs, then test and sort them into piles with the same voltage. They do that in China to make cheap white LED flashlights. Hey, use the matched LEDs from a flashlight.

    Why not connect a few LEDs in series then your current limiting resistor does not waste a lot of power making heat.
    Four 3.5V white LEDs need 14V then a resistor can be in series to limit the current with 3V across it
    if the LEDs are 2.8V then four need 11.2V and your current limiting resistor will have 17V - 11.2V= 5.8V across it.
    Four LEDs and a resistor are a string. Connect as many strings to the 17V as you want.
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
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    Jan 21, 2010
    Take a look here.

    That will tell you all you need to know without hyperbole.

    If your 17V is reasonably stable you should be able to put 3 or 4 LEDs in series with a single resistor and then just repeat that for as many LEDs as you require.
     
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