The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design >> Analog Design >> SNR simulation for Pre- Amp
https://designers-guide.org/forum/YaBB.pl?num=1159424884

Message started by packiaraj on Sep 27^th, 2006, 11:28pm

Title: SNR simulation for Pre- Amp
Post by packiaraj on Sep 27^th, 2006, 11:28pm

Hi,
I am doing a Pre-Amp (An OPAMP with resistive feedback) that would drive an ADC. The SNR requirement for whole chain is > 80 dB.

Now my quetion is, Is the input referred noise at the OPAMP input or the noise output at the output of OPAMP (input to ADC) important?

If I take Input referred noise then, How would I simulate this in Spectre, what to choose for Input source (Is it main input to the OPAMP?)

Thanks in advance,
Packiaraj V.

Title: Re: SNR simulation for Pre- Amp
Post by Sarig on Sep 29^th, 2006, 1:55pm

Hi,
You are designing an OPAMP with 80dB PSRR --> you should take care for noise else why such a high PSRR.
The question of Input or output noise is from what this OPAMP need to do. most of the time we look on input refered noise.
it is easy to see it by closing unity close loop and look at the output noise. this will give you the exact input noise which == output noise (unity close loop) if you have feedback which not 1 it will increase your input refered noise.
Goodluck
Sarig