| Author |
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mowhoong@hotmail.com
Guest
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 Posted:
Sat Nov 19, 2005 9:35 am Post subject:
One giga ohms resistor |
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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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Rheilly Phoull
Guest
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| Posted:
Sat Nov 19, 2005 3:38 pm Post subject:
Re: One giga ohms resistor |
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Perhaps they are making the worlds highest voltage 'Phase pencil' ??
--
Regards ......... Rheilly Phoull |
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Paul Burridge
Guest
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| Posted:
Sat Nov 19, 2005 5:03 pm Post subject:
Re: One giga ohms resistor |
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| Quote: | 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?
|
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
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Bob Masta
Guest
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| Posted:
Sat Nov 19, 2005 5:35 pm Post subject:
Re: One giga ohms resistor |
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On 19 Nov 2005 01:15:21 -0800, "mowhoong@hotmail.com"
<mowhoong@hotmail.com> wrote:
| Quote: | 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
|
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!
<g>
Best regards...
Bob Masta
dqatechATdaqartaDOTcom
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator |
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John Fields
Guest
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| Posted:
Sat Nov 19, 2005 5:35 pm Post subject:
Re: One giga ohms resistor |
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On 19 Nov 2005 01:15:21 -0800, "mowhoong@hotmail.com"
<mowhoong@hotmail.com> wrote:
| Quote: | 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?
|
---
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<---+
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[100K]
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GND
--
John Fields
Professional Circuit Designer |
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Michael A. Terrell
Guest
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| Posted:
Sat Nov 19, 2005 5:35 pm Post subject:
Re: One giga ohms resistor |
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"mowhoong@hotmail.com" wrote:
| Quote: |
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
|
I remember seeing them in some early B&W Vidicon type TV cameras.
--
?
Michael A. Terrell
Central Florida |
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John Fields
Guest
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| Posted:
Sat Nov 19, 2005 5:35 pm Post subject:
Re: One giga ohms resistor |
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On Sat, 19 Nov 2005 14:01:18 GMT, NoSpam@daqarta.com (Bob Masta)
wrote:
| Quote: | On 19 Nov 2005 01:15:21 -0800, "mowhoong@hotmail.com"
mowhoong@hotmail.com> wrote:
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
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),
|
---
Not always. I've got some 1000 megohm 1 watt resistors around here
somewhere in flat blue what looks like ceramic housings.
---
--
John Fields
Professional Circuit Designer |
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Steve Noll
Guest
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| Posted:
Sun Nov 20, 2005 12:31 am Post subject:
Re: One giga ohms resistor |
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On 19 Nov 2005 01:15:21 -0800, "mowhoong@hotmail.com"
<mowhoong@hotmail.com> wrote:
| Quote: | 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
|
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:
| http://www.big-list.com
| Peltier Information Directory:
| http://www.peltier-info.com |
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redbelly
Guest
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| Posted:
Sun Nov 20, 2005 1:34 am Post subject:
Re: One giga ohms resistor |
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Steve Noll wrote:
| Quote: | 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.
|
Or, I imagine, any application where small currents (as low as several
pA) are to be measured.
Mark |
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neon
Joined: 25 Feb 2006
Posts: 579
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| Posted:
Tue Mar 14, 2006 10:10 am Post subject:
Re: One giga ohms resistor |
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| redbelly wrote: | Steve Noll wrote:how you know you got a giga resistor a regular 11 mohms digital meter cannot do it. if i want something that large a gey a pencil paper and draw it
| Quote: | 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.
|
Or, I imagine, any application where small currents (as low as several
pA) are to be measured.
Mark |
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