Wondering what causes High speed in an opamp(closed loop).. I derived the step input for an closed loop single pole system to be
V0(1-e(-wf))
where wf is the closed loop bandwidth= wo(1+βAo)

where wo is open loop BW , Ao is open loop gain and β is feedback factor..

Is it good to approximate this wf to wo*β*Ao... considering wo << wo*β*Ao.

If I do this then the speed of the system depends on GBW and not BW.? But most of the books say speed depends on the BW(Rise time =0.35/BW).

Put it in another way
If I have an opamp1 which has say a BW of 300MHz and GBW of 1MHz and
and another opamp2 which has a BW of 500Mhz and GBW of 800Hz. Which is is faster pamp1 or opamp2?

Would appreciate enlightment on a simple (bothersome ) question?  

Thanks