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Noise due to passive resistor in Cadence Virtuoso

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deveshkm

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Hi,
I have used the resistors from the foundry, in the schematic.

I used res_typical (typical process for a resistor) in model libraries in Analog Design Environment of Cadence Virtuoso

For various feedback resistors, ranging from 1k -150k , I observed no change in the equivalent input referred noise of the amplifier.
(Input referred noise stayed fixed at 500 nV/√Hz)

Using the formula : 4kTR ,for Resistor thermal noise due to 150k ,
noise by 150k resistor is around 50 nV/√Hz

Do feedback resistors in opamp contribute to noise ?
Is Noise contribution only by those components , which are on the signal path?

Thanks
 

Please clarify the used circuit, does the resistor voltage actually add to the input? But even if it does, due to power summation, the 500 nV noise density only increases by 1 %.
 

Hi,

The resistors are used for providing the feedback factor. The amplifier is operating in the non-inverting configuration.
The feedback resistor does contribute to the output noise. However, the input-referred noise would be less due to hi gain.
Is noise-summary from ADE in Cadence Virtuoso, sufficient to be convinced?
 

Check your resistor properties, maybe it has a Noise Flag. If it is not ticked in the editor it won't generate noise under noise simulations.
 

The model of the resistor may be defined as "noiseless" or it might be an option.
 

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