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designing folded cascode OTA

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shobhit

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iam designing a fully differential folded cascode OTA
gain: 66 db
Vdd: 3.3 V
power dissipation 3.7 mW
BW: 980 Mhz
I have used switched capacitor CMFB(Common Mode Feed Back)

Problem: Iam getting gain of 54 dB and power dissipation of 2.7mW but the problem is that the gain curve is not crossing 0dB it reaches a minimum value of 1db at a frequency of about 14 MHz and then turns upward.It seems that multiple zeros are present but a far as I know there should be no zeros in folded cascode.............
Can any body help!!!!
 

hi shobit ..
can u tell me the design procedure
 

Hey there,

Can you upload or maybe describe how you set up your simulation?
 

shobhit, you can get a free reference design of OTA at :

**broken link removed**
 

i think you should have used 20*log(|(Vo1-Vo2)/(Vi1-Vi2)|) for gain calculation, if so done i too get the same result, but look only at the Vo1 ac plot it goes down to 0db so just calculate gain from Vi1 to Vo1 if you are using it in fully differential mode,it doesn't make any difference.
 

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