relation between settling time and UGB

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what is 3db bandwidth and ugb

hi i am desinging an ota for pipelined adc of 12.5ns settling time .
what should the gain and UGB of this OTA.
what is the relation between settling time and UGB.
plz clearify me ..
waiting for ur reply ..
manish
 

Settling time Ts=t*LN(1/e)

t - timeconstant

t=1/2*π*BW=Av/2*π*GBW= if PM≈70°

e - coefficient of settling the output signal in percents!
 

hi ur equation
t=1/2*n*BW
what is the n signifies..in above equation..
and t=Av/2*n*GBW
here what is A ( is it gain)
plz clearify it ..
manish
 

Hi,

π-this is pi=3.14

Av- open loop gain.
 

Assuming this is first order system. The settling time is related to the 3dB Bandwidth. the time constant is 1/W3db. So, Ro*C is the time constant.
Once your OTA is used in feedback system, the settling time depends on the
feedback sturcture, β*ωt.
 

settling time is also reletated to feedback factor of your opamp if you dont use the opamp in unitgain buffer, you can also google some papers !!!
 

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