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Voltage Regulator/ Voltage Reference

Discussion in 'Electronic Basics' started by GraemeC, Mar 22, 2007.

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  1. GraemeC

    GraemeC Guest

    Im trying to create a +/- 2.5V supply from a +/-5V. I have a couple
    of 2.5V voltage references. Am I right in assuming that I need to get
    hold of a -2.5V reference? I did read an article that showed how I
    could use an inverter but I don't have any of those either.

    There seems to be a gap in my knowledge because I don't really
    understand the difference between a voltage reference and a voltage
    regulator.

    Thanks

    G
     
  2. If your 2.5 volt references are shunt type (two terminals
    that hold 2.5 volts when an externally limited current is
    passed through), you can use two of them to regulate a small
    (milliamperes) supply. If you want a more significant
    current from these supplies, you should use actual supply
    regulators. The adjustable LM317 and LM337 pair can be set
    to 2.5 volts output with a pair of resistors.
    http://www.fairchildsemi.com/ds/LM/LM317.pdf
    http://www.fairchildsemi.com/ds/LM/LM337.pdf
     
  3. You need a low-impedance driver set at 2.5V relative to your current
    ground and this new low impedance driver needs to source or sink
    (two-quadrant, if my hobbyist knowledge of terms is close to right.)

    You don't say what your _current_ requirements will be. There's a
    simple answer if you are talking about a few tens of mA. This is the
    TLE2426 "rail splitter." Also, an opamp set up with the 2.5V
    reference to its (+) input and its (-) tied to its output, which
    drives the new center point "ground" might be okay, assuming your
    opamp can deliver the current requirements you are looking for. (Or
    just use a resistor divider instead of the 2.5V reference, to the (-)
    input.) A discrete splitter could be formed out of transistors, too.
    A reference usually has a very small _current_ drive capability -- not
    uncommonly in microamps -- to name one important difference.

    Jon
     
  4. Sorry, I meant (+), not (-).

    Jon
     
  5. Jamie

    Jamie Guest

    use a 2425 and turn it around.
    the COM will be the - line and (IN) your common .
     
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