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Virtual Ground.

Discussion in 'Electronic Design' started by Jamie, Nov 12, 2006.

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  1. Jamie

    Jamie Guest

    I have here, a component from
    TI,
    The number on it as marked "2425C", all info
    found leads to being a Virtual Ground device
    with IN, COMMON, out..
    the example spec's are
    5V in, 2.5 out.
    now i understand the use of virtual grounds in systems
    that do not have a real - rail and is not using a
    DC-DC to derive it. what i would like to know is, a simple
    use/configeration for this device so that i can better understand
    it's operations.
    Virtual grounds that i have worked with before in the past used
    zener diodes that feed the - side of the bridge through these
    ZENERS that would connect to the main common. this way, components
    that needed some - voltage (in effect of), would simply connect it's
    - rail to some point in this Zener diode chain to obtain the desired
    zener voltage. this of course, reduces the amount of V you get on the
    + rail.
    in using one of these TI2425C/ TLE2425CN etc...i would like to know
    how a simply wiring to obtain some - rail voltage.
    the PDF doc TI supplies does not show a test circuit, and it only
    mentions 5 VOLTS in and 2.5 out.
    i can only assume that, the INPUT maybe from the - side of the supply,
    common to the main common and output would be the - rail voltage of lets
    say 2.5 volts ?
     
  2. The common terminal goes to a ground or a negative supply, the input
    terminal goes to a positive voltage supply, so that the total voltage
    from input to common is less than the 2425s rating input voltage
    rating. Then you get +2.5V on the output terminal w.r.t. the common
    terminal. It's just a precision 3-terminal regulator. The 2.5 V unit
    would usually be used in a system with a single 5 V supply, to get a
    virtual ground for analog circuits at V+ / 2.
     
  3. This may help:
    http://focus.ti.com/lit/an/slaa064/slaa064.pdf

    Richard
     
  4. Your post is a bit rambling, but
    I havent read the TI doc, but the main difference is that the VG will
    split the supply by two, so if the supply drifts a bit, eg a car
    battery, it will always be 1/2 the supply.
    With a zenered VG it will remain at the Vz, so as the supply varies,
    the psuedo + - supplies will not be symetrical

    hope this helps


    martin
     
  5. The TLE2425 is basically a 2.5 volt voltage regulator - the input is
    +5 volts, and the output is +2.5 volts. It does not generate a
    negative voltage.

    The idea of the thing is that you can operate your analog circuit on a
    single +5V supply (just +5 and ground), and the TLC2425 will produce a
    stable +2.5 volts that will connect to the points in your circuit that
    would go to ground if you were using a bipolar supply (like +5 and
    -5).

    --
    Peter Bennett, VE7CEI
    peterbb4 (at) interchange.ubc.ca
    new newsgroup users info : http://vancouver-webpages.com/nnq
    GPS and NMEA info: http://vancouver-webpages.com/peter
    Vancouver Power Squadron: http://vancouver.powersquadron.ca
     
  6. Ban

    Ban Guest

    It is IMHO a pretty useless part with an awful lot of noise. You can
    configure almost any opamp to sink and source 20mA and a voltage reference
    to do the same. Only certain ADCs with a single reference and low speed can
    make advantage of this IC, for opamps it is better to just use a voltage
    divider for the reference voltage. If you had read the datasheet, you would
    know that it is powered fro either the +5V rail or higher.
     
  7. Eeyore

    Eeyore Guest

    And you think you're clever ?

    The 2.5V out is your virtual ground.

    Graham
     
  8. Jamie

    Jamie Guest

    thanks, that cleared it up, i also found a sight that was helpfull.
    http://tangentsoft.net/elec/vgrounds.html

    i understand the practice of doing so,i just have never seen that done
    in a single package with no components like that.
     
  9. Eeyore

    Eeyore Guest

    It's an *integrated circuit* FFS !

    Graham
     
  10. Jamie

    Jamie Guest

    I think you have some complex personality issues
    that needs serious attention.

    I hate like hell to lower my self to your standards!
    giving out advice on one's mental condition and suggesting
    help is not usually something i enjoy doing.

    You should give your NHS a call and explain your condition.
     
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