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9th June 2019, 16:43 #1
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How to calculate the inputrefered noise for two OTA in parallel?
Hello
I'm a bit unsure on how to calculate the inputrefered noise for two OTA in parallel.
Lets say that both OTA have a input referred noise level of Vn = 60 nV/sqrt(Hz) individually.
I have read that if I regard two noise sources connected in series as uncorrelated i can add them.
If i connect the two OTAs in parallel and refer the noise to the input, will the noise become bigger or smaller?

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9th June 2019, 17:26 #2
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Re: How to calculate the inputrefered noise for two OTA in parallel?
Output noises are uncorrerated.
So input reference noise is 3dB down.
Gm is twice.
On the other hand, Iout_noise is by sqrt(2).Last edited by pancho_hideboo; 9th June 2019 at 17:41.
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9th June 2019, 17:56 #3
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Re: How to calculate the inputrefered noise for two OTA in parallel?
So according to theory the resulting input refered will be reduced by half to 30 nV/sqrt(Hz)?
The reason why i'm asking is that im simulating the individual stages to be 58 nV/sqrt(Hz) and 67 nV/sqrt(Hz) individually.
And when im simulating them in parallel i get 56 nV/sqrt(Hz).
Does that sound reasonable?

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10th June 2019, 00:39 #4
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Re: How to calculate the inputrefered noise for two OTA in parallel?
Last edited by pancho_hideboo; 10th June 2019 at 00:47.
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10th June 2019, 11:41 #5
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Re: How to calculate the inputrefered noise for two OTA in parallel?
I see, I understand it now.
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