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One giga ohms resistor

Discussion in 'Electronic Basics' started by [email protected], Nov 19, 2005.

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  1. Guest

    A customer next to me asking the shop assistant whether he sells one
    giga ohm resistor.
    I am wondering what is the pupose to use such a high resistance
    component, this is almost
    a good insulator for any material like plastic. Dear member, does any
    person know the reason for buying a 1 giga ohm resistor?
    Best Wishes and merry x'mas
  2. Perhaps they are making the worlds highest voltage 'Phase pencil' ??
  3. The very high input impedance of MOSFET stages often specify these
    very high value bias resistors, IIRC. Helps to prevent loading down
    previous hi-output impedance stages.
  4. Bob Masta

    Bob Masta Guest

    I've seen very high resistors used as feedback in
    sensitive photodetector and electrometer-type circuits.
    Biggest I ever used was 100 Meg, and even at that
    it was non-trivial to actually get the resistance you
    paid for. The problem is that it doesn't take much
    leakage current to knock down these high values
    in the actual circuit. You need to be fanatical about
    cleaning the outside of the glass resistor body (these
    are always in glass bodies), since any sort of film
    will cause leakage. You need may exotic circuit board
    and teflon mounts, etc, etc. And it's hard to know
    when things have gone wrong, since you typically
    don't have a femtovolt or picocandela calibration source!

    Best regards...

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Home of DaqGen, the FREEWARE signal generator

  5. I remember seeing them in some early B&W Vidicon type TV cameras.
  6. John Fields

    John Fields Guest

    I've used them as part of the feedback voltage divider in regulated
    high voltage power supplies.

    ----+---->10KV OUT
  7. John Fields

    John Fields Guest

  8. Steve Noll

    Steve Noll Guest

    They are used as feedback resistors in photodiode transimpedance
    amplifiers (current to voltage converters.) One nanoamp into an op
    amp with a 1 G feedback resistor comes out as one volt.

    I Gigohm's are even available in chip form and in 1% tolerance. I
    have used as high as 10 Gigohm 1% resistors in photodiode test
    equipment. Victoreen, now owned by Ohmite, is one manufacturer.
    Digi-Key carries them through 5 gig 1%.

    Steve Noll | The Used Equipment Dealer Directory:
    | Peltier Information Directory:
  9. redbelly

    redbelly Guest

    Or, I imagine, any application where small currents (as low as several
    pA) are to be measured.

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