Telescopic opamp for wimax adc aplication

Hi I'm designing a telescopic opamp for wimax adc aplication.

Important Spec
Bandwidth : >> 40Mhz
Gain : 50dB
PM : 60 70 degree

I have no problem getting the gain and the PM...but to get the 40MHz bandwidth quite a problem.

All calculation are done user 1st order formula....Can help me with more accurate calculation.

My model use BsimV3.

50 dB = 316
Ft = 316 x 40M = 12.6Ghz

GBW = 1/2*pi*gm*Cl Cl = 1p

I can get the gm then the current...the problem my ft never hit 12.6GHz

I only get around 1Ghz.

Please let me know if you want more info.


Another solution that i try is to do 2 stage by adding another class ab amplifier
Please refer to GBW.jpg

By adding another stage I can design a lower gain for each stage....but does not make sense because telescopis topology is good for hi gain.


Please give some suggestion:
How to get 40Mhz bandwidth
How to decrease the internal capacitance
Are solution no. 2 is a good choice


Thanks for helping