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10th May 2008, 15:37 #1
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switch capacitor integrator
hi :
I have a question about switched capacitor integrator.
The integrator was constructed from a folded cascode opamp ,
which have common mode feedback.
If i give a "dc" input signal , what will i see at opamp output?
the output voltage will accumulate form the common mode voltage?
or keep at common voltage?
Because i try to use this way to find the opamp gain, is it correct?
(From the transfer function (z=1, DC), can get the finite gain of opamp)
thanks

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11th May 2008, 04:37 #2
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Re: switch capacitor integrator
the output of integrator will step up if you apply a positive dc input. if you use fullydifferential structure, the commonmode voltage of two outputs of opamp will be maintained on what you set by commonmode feedback.
this is a method to find the finite gain of opamp. in general, i simulate the gain of opamp in frequency domain by applying ac small signal to the input of opamp.

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11th May 2008, 06:36 #3
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Re: switch capacitor integrator
Thanks for your reply :
Do you mean if i use fullydifferential structure,
the output of integrator will not step up if i apply a positive voltage?
But will set by common mode voltage, so i need to simulate it in frequency domain.
thanks

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11th May 2008, 06:52 #4
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Re: switch capacitor integrator
Originally Posted by crazyfox
as for the opamp gain, using ac small signal method to simulate the openloop response of opamp.
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16th May 2008, 03:26 #5
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Re: switch capacitor integrator
Originally Posted by crazyfox
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