Is there negative Voltage References?

Discussion in 'General Electronics Chat' started by PSIR, Feb 28, 2011.

  1. PSIR

    Thread Starter Member

    Apr 23, 2008
    29
    0
    Hi Everyone,

    Is there negative Voltage References?
    I am looking for -2.5V Voltage Reference IC.
    Can anybody recommand part number or brand of a product to me.

    Best Regard
     
    Last edited: Mar 1, 2011
  2. jut

    Senior Member

    Aug 25, 2007
    224
    2
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    That's not a reference, it's a regulator. Regulators generally are not as precise or as stable as references. Also, references are not designed to carry significant current.

    If you know how to use a zener as a negative reference, you can use a shunt reference IC (2 or 3 pin) the same way.
    Series references (at least 3 pins) are generally positive output devices, but they can be used as negative references. See AN42 from Linear technology for some ideas.
     
  4. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    How do you get a negative reference when all there is to work with is positive voltages
     
  5. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    You can also use the TL431, connected in this way.

    [​IMG]
     
  6. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
    47
    You can use a positive reference and a unity gain inverter.
     
  7. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    That illustrates the point I made about knowing how to use zeners as negative references.
     
  8. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    I suggest you Google this phrase negative voltage reference. Then select a few options. And take them back here for comments. Remember always to check availability and package type before you made your final design.
     
  9. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    Too simple!

    The TL431 circuit shows (+) power at ground and the (-) power feeding the circuit. That is not possible if you only have one positive supply to work with that has (-) at ground, like normal.

    Look at the LM317/350/338 data sheets for making adjustable regulators. Their adjustable output starts at +1.25 volts. If you need to start at 0 volts, you need a negative voltage to supply -1.25 for the regulator which you can't get with a negative grounded supply.

    So far, a small switching inverter like a MC34063 is as close as I can get to cheap, simple, compact reversed power.
     
    Last edited: Mar 1, 2011
  10. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    Clearly, if there is no existing negative supply one would need to be created, either at the desired reference value, or a more negative value to allow for regulation.

    Perhaps the OP merely had difficulty understanding that a typical shunt reference device can be used for either polarity, given suitable supply rails.
     
  11. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    By the way. Why do you need a negative reference? Can your problem be solved with a common positive reference and a summing opamp configuration.
     
Loading...