spectre PSS/Pnoise on Sampling & Hold Circuit

Guest
I have run a PSS/Pnoise analysis for my sampling & hold circuit. The
structure of circuit is switched capacitor, flip around with a
gain-boosted amplifier. When printing noise summary, I found the top 8
noise contributers (they generated 70% of total noise) are not from
main amplifier, but from gain boost amplifier (AUX amplifier). It's
pretty much way out of my imagination, the noisy amplifier is on the
signal loop though. My PSS/Pnoise setting up are like following:

PSS: 80M beat frequency, number harmonics: 20; time of stable: 300n,
maxacfreq: 1.6G
Pnoise: start: 1, stop: 40M (Nyquist); Max Sideband: 20; Timedomain:
time point 7.1n (hold end point)

To interpret the Pnoise results, I did a noise analysis with a linear
test bench for amplifier (main amplifier with AUX one) only, there most
noise contributers are input and current soure transistors at main
amplifier. It's very interesting that AUX amplifier has shown almost
nothing with total noise this time. Does anyone has any idea with it?
Thanks a lot.


Regards

Vincent
 
Could you give more definition on what you mean by "gain-boosted
amplifier"? Do you mean an amplifier employing a gain-boosted cascode
device?

On Jan 17, 7:08 am, hb_hu...@hotmail.com wrote:
I have run a PSS/Pnoise analysis for my sampling & hold circuit. The
structure of circuit is switched capacitor, flip around with a
gain-boosted amplifier. When printing noise summary, I found the top 8
noise contributers (they generated 70% of total noise) are not from
main amplifier, but from gain boost amplifier (AUX amplifier). It's
pretty much way out of my imagination, the noisy amplifier is on the
signal loop though. My PSS/Pnoise setting up are like following:

PSS: 80M beat frequency, number harmonics: 20; time of stable: 300n,
maxacfreq: 1.6G
Pnoise: start: 1, stop: 40M (Nyquist); Max Sideband: 20; Timedomain:
time point 7.1n (hold end point)

To interpret the Pnoise results, I did a noise analysis with a linear
test bench for amplifier (main amplifier with AUX one) only, there most
noise contributers are input and current soure transistors at main
amplifier. It's very interesting that AUX amplifier has shown almost
nothing with total noise this time. Does anyone has any idea with it?
Thanks a lot.

Regards

Vincent
Click to expand...
 
On 17 Jan 2007 05:08:59 -0800, hb_huang@hotmail.com wrote:

I have run a PSS/Pnoise analysis for my sampling & hold circuit. The
structure of circuit is switched capacitor, flip around with a
gain-boosted amplifier. When printing noise summary, I found the top 8
noise contributers (they generated 70% of total noise) are not from
main amplifier, but from gain boost amplifier (AUX amplifier). It's
pretty much way out of my imagination, the noisy amplifier is on the
signal loop though. My PSS/Pnoise setting up are like following:

PSS: 80M beat frequency, number harmonics: 20; time of stable: 300n,
maxacfreq: 1.6G
Pnoise: start: 1, stop: 40M (Nyquist); Max Sideband: 20; Timedomain:
time point 7.1n (hold end point)

To interpret the Pnoise results, I did a noise analysis with a linear
test bench for amplifier (main amplifier with AUX one) only, there most
noise contributers are input and current soure transistors at main
amplifier. It's very interesting that AUX amplifier has shown almost
nothing with total noise this time. Does anyone has any idea with it?
Thanks a lot.


Regards

Vincent
Click to expand...
I think it's quite difficult to know what the problem is (assuming there is a
problem) from just your very high level description of the circuit (I can't
picture what it looks like from your description, for example). Probably the
thing to do is to contact Cadence customer support with your testcase, and an AE
can help you interpret the results.

Best Regards,

Andrew.
--
Andrew Beckett
Principal European Technology Leader
Cadence Design Systems, UK.
 
Thanks Poojan. My circuit is a quite typical folded cascode amplifier
with pmos input. There are two AUX amplifiers working as gain booster
on cascode NMOS and PMOS, respectively.

There are several questions I want to figure out:

1. If I can count on PSS/PNoise analysis for the noise estimation?
Considering my circuit is working as switched capacitor way, looks like
I don't have so many choices to get noise info. Also, this circuit is a
Sampling & hold frount end stage for pipeline A/D, the next stage is
working as switched capacitor circuit too.
2. Is it correct that I choose "timedomain" within PNoise analysis? and
time point (for timedomain analysis) is same as S/H's holding end point
? should I change it to other kind of noise format within PNoise
analysis, like modulation, jitter or source?
3. In this case, what's the physical meaning of PNoise's output? Is it
really represent noise within this system?


Regards


Vincent

"Poojan Wagh Đ´ľŔŁş
"
Could you give more definition on what you mean by "gain-boosted
amplifier"? Do you mean an amplifier employing a gain-boosted cascode
device?

On Jan 17, 7:08 am, hb_hu...@hotmail.com wrote:
I have run a PSS/Pnoise analysis for my sampling & hold circuit. The
structure of circuit is switched capacitor, flip around with a
gain-boosted amplifier. When printing noise summary, I found the top 8
noise contributers (they generated 70% of total noise) are not from
main amplifier, but from gain boost amplifier (AUX amplifier). It's
pretty much way out of my imagination, the noisy amplifier is on the
signal loop though. My PSS/Pnoise setting up are like following:

PSS: 80M beat frequency, number harmonics: 20; time of stable: 300n,
maxacfreq: 1.6G
Pnoise: start: 1, stop: 40M (Nyquist); Max Sideband: 20; Timedomain:
time point 7.1n (hold end point)

To interpret the Pnoise results, I did a noise analysis with a linear
test bench for amplifier (main amplifier with AUX one) only, there most
noise contributers are input and current soure transistors at main
amplifier. It's very interesting that AUX amplifier has shown almost
nothing with total noise this time. Does anyone has any idea with it?
Thanks a lot.

Regards

Vincent
Click to expand...
 
On 18 Jan 2007 04:36:45 -0800, hb_huang@hotmail.com wrote:

Thanks Poojan. My circuit is a quite typical folded cascode amplifier
with pmos input. There are two AUX amplifiers working as gain booster
on cascode NMOS and PMOS, respectively.

There are several questions I want to figure out:

1. If I can count on PSS/PNoise analysis for the noise estimation?
Considering my circuit is working as switched capacitor way, looks like
I don't have so many choices to get noise info. Also, this circuit is a
Sampling & hold frount end stage for pipeline A/D, the next stage is
working as switched capacitor circuit too.
2. Is it correct that I choose "timedomain" within PNoise analysis? and
time point (for timedomain analysis) is same as S/H's holding end point
? should I change it to other kind of noise format within PNoise
analysis, like modulation, jitter or source?
3. In this case, what's the physical meaning of PNoise's output? Is it
really represent noise within this system?


Regards


Vincent
Click to expand...
I'd suggest reading:

http://www.designers-guide.org/Analysis/sc-filters.pdf

the netlists are available at:

http://www.designers-guide.org/Analysis/sc-netlists.zip

if you need them.

This is a good overview of using SpectreRF to simulate switch cap circuits, and
will probably answer your questions.

Regards,

Andrew.
--
Andrew Beckett
Principal European Technology Leader
Cadence Design Systems, UK.
 
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