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op amp feedback resistor

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bigsamoncampus

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Apparently, there is some discrepency in texts regarding whether increasing the feedback resistor in an op-amp will increase the total noise or not.

Does anyone know whether the noise stays constant, increases or decreases when the feedback resistor, Rf, is increased or decreased? Or where I could find info on the topic?

Thanks for the help.
 

For Rf <=> noise relationship see:
**broken link removed**

Regards,
IanP
 
for both inverting and non inverting configuration,gain depends upon feedback resistance.it is obvious, if feedback resistance increases then gain will also do same thing and samething can be extended for decreasing feedback resistance....for a system if gain increases,then noise will be also amplified.so that conclusion is feedback resistance influences the noise. correct me if i am wrong
 
hi dear,

I THINK YOU ARE RIGHT
 

Well, there are several noise sources, internal to the chip or op-amp and externalr like the resistor, ans ambiental noise that contaminate your signal.
If your gain is high the noise will be visible at the output.
 

If you keep your values low, you get a better noise peformance, as less noise voltage is generated by the random movement of electrons.
 

the noise of any amplifier is generated at the input source PERIOD. the feedback resistor can only amplify the noise or reduce the noise depends on the vakue. a good amplfier usualy has a 90 DB moise rejection from power supply so the [enviroment] whatever that is has very little to do with it. the noise is not accumulative by stringing amps after amps it will be the same as the except for gains introduced
 

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