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help in op amp design

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wael_wael

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hi every body
could some one help me to find value of R & C in this circuit or help me to analysis it.
thanks in advance
 

sunking

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the value RC depond on your load,too.

Refenece the book:
cmos analog circuit design
 

    wael_wael

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eezou

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What's your specifications? RC values is determined by your specs.
 

    wael_wael

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pfd001

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The RC value is dependant on the load capacitance
 

    wael_wael

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wael_wael

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sunking said:
the value RC depond on your load,too.

Refenece the book:
cmos analog circuit design
firstly thanx all
i have this book but i couldnt find the same circuit, i hop you can help me
thanx in advance
note
i will use it for pipeline ADC
 

qutang

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the r&c 's value depend on your transistor's size.
 

    wael_wael

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rfsystem

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The R of the RC puts an additional zero in the compensation network. This zero should be matched to a parasitic pole coming from the folded cascode. The M21/M22 have a transconductance (gm in DCOP result file) which make with the CGS and CSB and other caps there a parasitic pole. Because this pole is bias and tech dependend most often the R is made of an NMOS and matched to the gm above.

By the way the common voltage of the differential folded cascode is undefined. There two unrelated pairs of curent sources act against!
 

    wael_wael

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zenisle

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the R C value depand on your phase margin requirement.
 

    wael_wael

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wael_wael

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if found the soltion, if any body intrest
pls, download this paper
regds
 

wjlzhx

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i think Cc=0.2CL
and the r= 1/gm51
 

    wael_wael

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wael_wael

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could some one help me to find v bias
regds
 

nuiscet

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R=1/gm51 to cancell the Influence of the zero point and C depends on the load capacitor and the ratio of the first stage amplifier gain and the second stage amplifer.usually we take the factor of 2~3 .
 

    wael_wael

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airboss

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hey,

i'm sorry to tell you that this paper is crap. i read this paper before. i useed all of the parameters and sizing the author used but i didnt get what he has on this paper.

btw, are you designing a telescopic or a folded cascode?
 

wael_wael

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Added after 1 minutes:

airboss said:
hey,

i'm sorry to tell you that this paper is crap. i read this paper before. i useed all of the parameters and sizing the author used but i didnt get what he has on this paper.

btw, are you designing a telescopic or a folded cascode?
yes i am designing telescopic op amp, could you help me?
do u mean this paper
"a 1.0v 10b 100 MS/s pipeline ADC in 90 nm cmos"
 

ee484

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wael_wael said:
hi every body
could some one help me to find value of R & C in this circuit or help me to analysis it.
thanks in advance


Sometimes...R value might not need it. (potentially with more power consumption, but negligibly small)
C should be determined by understanding between 1st and 2nd stage power consideration.
For example, if C is large, it splits poles farther apart (thus, better in stability), however, 1st stage needs lots of power to have reasonable bandwidth.
R value is easy to determined....R is used to push a right half plane zero to left half plane zero or to the infinity.
 

airboss

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yes i am designing telescopic op amp, could you help me?
do u mean this paper
"a 1.0v 10b 100 MS/s pipeline ADC in 90 nm cmos"
**************************************************
Hi,

711_proj.pdf isn't a good reference.

you need help with sizing the fets? it would be better if you post out the power supply and Vov you assign for each of the transistor.
 

    wael_wael

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wanily1983

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i agree with wjlzhx. R is used to cancel the zero caused by the miller cap.
 

wael_wael

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R=CL+CE+CC/(gm1*CC)
CE=800fF
regds
Note
 

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