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 regards
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I\'ve used them as part of the feedback voltage divider in regulated
high voltage power supplies.
----+---->10KV OUT
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[1GR]
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1V
-- Not always. I\'ve got some 1000 megohm 1 watt resistors around here somewhere in flat blue what looks like ceramic housings.
Or, I imagine, any application where small currents (as low as several pA) are to be measured.
Mark
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.
-- "What is now proved was once only imagin\'d" - William Blake
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 dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis
I remember seeing them in some early B&W Vidicon type TV cameras.
-- ? Michael A. Terrell Central Florida
Perhaps they are making the worlds highest voltage 'Phase pencil' ??
-- Regards ......... Rheilly Phoull
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: |
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