Stats

Locked Locked
Replies 4
Subscribers 126
Views 17520
Members are here 0

This discussion has been locked.

You can no longer post new replies to this discussion. If you have a question you can start a new discussion

How do you simulate the input referred noise for a chopper amplifier?

Hi,

trying to simulate a chopper amplifier. For testing it is configured as a voltage follower. There is only one clock all the non overlapping clocks ect are derived from it. The problem is that the flicker noise is not being reduced on the input noise plot when I use the following pnoise, pss settings:

pss pss fund=100k harms=3 errpreset=conservative
+    annotate=status
pnoise ( out 0 ) pnoise sweeptype=relative relharmnum=1
+       start=1 stop=50k log=20 maxsideband=20 iprobe=V2 refsideband=0
+       annotate=status

I have tried various settings and cannot reduce the flicker noise. I have verified that the chopper is working and it does remove the dc offset when inserting a non zero vdc at the inputs in the time simulation. I have also tried following the chopper opamp with a with a sample and hold and taking the output for pnoise simulation from the sample and hold but this still does not reduce the flicker noise seen on the direct plot.

I've read Ken Kundert's sc-filters.pdf from www.designers-guide.org/Analysis/ and have successfully used pss and pnoise to simulate an oscillator in the past following the spectreRF tutorial.

There has been a few posts on this site as well as others but the only advise given is to eternally point people to Ken Kundert's sc-filters.pdf or the cadence manual.

Any ideas where I'm going wrong with the simulation setup?

Regards,

harmonics

BenMartin over 14 years ago

I have the same question. I don't see 1/f noise being modulated away from the origin. Did you ever figure it out? Ben
Cancel
Vote Up 0 Vote Down

Cancel
harmonics over 14 years ago

BenMartin said:
I have the same question. I don't see 1/f noise being modulated away from the origin. Did you ever figure it out? Ben
It should be set to the zero harmonic ie relharmnum=0 not relharmnum=1 as that starts the sweep around the clock (see my original spectre settings above) which was not the intention. After that the settings are fine and the chopper works as desired regarding 1/f noise.
The error was obvious but no thanks to this forum though.
Cancel
Vote Up 0 Vote Down

Cancel
Andrew Beckett over 14 years ago

Sorry, been rather busy over the last few weeks and did not have a chance to read this through carefully and spot the error. Unfortunately the symptoms weren't that clear, but you're right - it's an obvious mistake, since the input and output frequency of the amplifier are the same.
Regards,
Andrew.
Cancel
Vote Up 0 Vote Down

Cancel
BenMartin over 14 years ago

Thank you!
Cancel
Vote Up 0 Vote Down

Cancel

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.