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Need high mega ohm of resistor , please help me , thank you

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amazonite

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can you mega ohm resistor op amp

I want to design an amplify circuit , and I need about 500M ohm of resistor in my design. But I don't know how to buy it form ? Please tell me the company's name if you know. My E-mail is bearchang@gmail.com . Thank you.
 

Davood Amerion

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50 megaohme resistance

Hi,
What is your circuit which need this high value resistor :D:?:
I am not sure this high value resistor available in market.
but i think you can series some of them with lower value. you may found 22M or 10M but you must series 23 or 50 of them :cry:

another thing:
any material have it's resistance, with this high value any mateial may behave such resistor.
 

echo47

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22 mega ohm

Search Google for "high value resistors" and you will find many manufacturers. For example, IRC:
http://www.irctt.com/pdf_files/HR.pdf

If you need high voltage capability, then search for "high voltage resistors".
 

Chethan

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mega ohm resistors

amazonite said:
I want to design an amplify circuit , and I need about 500M ohm of resistor in my design. But I don't know how to buy it form ? Please tell me the company's name if you know. My E-mail is bearchang(at)gmail.com . Thank you.
These are some of the companies which sell resistors of that high values
General Atomics Energy Products
International Manufacturing Services, Inc
ITT, Power Solutions
Onlinecomponents.com
Piconics, Inc
RCD Components, Inc
RFE International, Inc
Rohm Electronics
EBG, LLC
Honeywell SSEC


regards
Chethan
 

Kral

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Re: Need high mega ohm of resistor , please help me , thank

amazonite,
Depending on your amplifier application, this might help. If the resistor is used as the input resistor or feedback resistor in an inverting amplifier, consider using a "Tee" network. Let R1, R2 be the series resistors, R3 the shunt resistor in the "Tee". The equivalent resistance is given by the equation
~ Req = R1 + R2 + R1R2/R3
By setting R3<<R1, R2, you can get a high value equivalent resistance without using high value resistors. The equation works for any application where both ends of the "Tee" are at ground or virtual ground. It does not work for a non-inverting OP Amp amplifier application.
~
One caveat; High humidity, as well as contaminants, can drastically affect the resistance value of a resistor with this high value of resistance.
Regards,
Kral
 

throwaway18

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>consider using a "Tee" network

In his column in Electronic Design magazine Robert Pease says "Often, an engineer proposes to use a "tee network" for his feedback resistance to avoid having to buy a large-value resistor. I almost always say that that's a bad idea. Why? Because of the noise gain! Either due to the noise, or the bandwidth, or the drift, any tee network with a factor of more than 2 is usually a terrible idea."

http://www.elecdesign.com/Articles/Index.cfm?ArticleID=7164

I don't entirely understand this. Does it apply here?
 

tzoupkas

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use the T network with the follow resistors R1=R2=1M and R3=2K+8ohm. but what kind of desing needs such high res?
 

Kral

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Re: Need high mega ohm of resistor , please help me , thank

Regarding noise gain; yes, it does apply here. The noise gain will be high whether we use a Tee or not, assumming you are looking for a high closed loop gain. In addition there are other problems. In an inverting amplifer, the output error due to Vos is Vos(Rf + Ri)/Ri = VosRf/Ri + Ri/Ri = Vos[1 + (Closed loop gain)]. With a Tee netwoerk the output error is higher, because of the voltage divider action of the Tee with respect to the inverting input. I don't remember the equation, but if anyone wants it, please respond, and I'll either dig it up or derive it.
Regards,
Kral
 

jinxingsun

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If you are designing a integrated circuit ,you can use a sc circuit to simulate this large value resistor.
 

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