How to simulate a switched capacitor circuit?

[moisiad]

switch capacitor circuit

Hi all
I want to simulate a folded cascode OPAMP with a discreate Common Mode Feedback circuit. The problem is that i can not run an AC analysis directly, as the CMFB circuit must run first in transient analysis in order to establish the DC voltage that control the current sources in the OPAMP.

How to we overcome this problem?

 

[mists]

simulating switched capacitor circuits

switcap and spectra can run AC character of switch capacitor circuit.

 

[wjxcom]

switch capacitor

I have the same question, and I know switcap and spectra can run AC character of switch capacitor circuit,but now the question is how to simulate?

 

[Chung-Yuan Chen]

how to simulate switched capacitor circuits

The first, you must model the discrete type CMFB as an amplifier by using E cell (SPICE). Then, you can simulate the loop gain and phase margin of the CMFB network. The stability and loop gain is very important even then the discrete type CMFB is almost unconditional convergent. But the ratio of the two capacitors will influence the rate of convergence.

 

[moisiad]

pac phase margin switched cap

Do you believe that the following methodology will give correct results ? :

First to run a transient analysis to see the value of the bias voltages generated by the switched capacitor network, and then an AC analysis with this values given to the OPAMP as ideal voltage sources.

Waiting for your reply

 

[sunking]

simulating switched-capacitor

run spectre in ic50
.pss
.pac

 

[Chung-Yuan Chen]

transient analysis of switching capacitors

Hi ,Moisiad
I believe that the general methodology will give correct results, but you will over design your opamp very much. Discrete type CMFB is very powerful so the general methodology will give correct results.

 

[xwcwc1234]

pxf simulate

To Chung-Yuan Chen,
How to simulate the CMFB' pahse margin and gain if I use Hspice ?

 

[wylee]

why switched capacitor

sunking,

can you teach us how to check phase margin of a swtiched capcitor circuit using Cadence? Detailed steps of a case study is preferred...

 

[hr_rezaee]

switch capacitor

use APLAC.

 

[beckchm]

switch capacitor spectre problem

nobody can explain so clearly

 

[beckchm]

simulating a switched capacitor circuit

what is .pss

 

[jerryzhao]

circuit with switch and capacitor

I use the E source .
u can lookup the menu of hspice.
u must know the relation between the CMFB and op.
The capacitor like a battery or voltage source.
So the E source maybe :
EXX net1 net2 v=(.....)

 

[wdd]

switched-capacitor circuits

run spectre in ic50
.pss
.pac

can you share some documents about how to use .pss and .pac?

 

[hanm]

how to simulate switched capacitor filter

Search in goole,first!

 

[mark_nctu]

cmfb switcap

See the link : https://www.designers-guide.org/Analysis/

 

[basilyb]

switched capacitor circuit

there are some questions with .pss .pac/.pxf when simulating switched capacitor filter.
firstly, the input signal must be a dc signal with only clock pluse for pss .
secondly, the input signal is set to a ac singal for pac, but pss's some parameter is changed, so the first pss simulation is ok for pac?