Open loop Vs Closed Loop

[safwatonline]

i see that Open loop amplifiers are being used in pipelined ADCs with the claim that they reduce the Power Consumption, can anyone justify this.
what i was thinking about is that we say need Gain G and BW B in closed loop so that the effective gain will be say G/(1+G*beta) and the BW will be B*(1+G*beta), while in open loop i need the same effective gain and BW , so eventually i need the same GBW!
p.s. i am not concerned about accuracy, linearity just the Power consumption.

 

[ce]

I can think of one possible reason:

In a closed loop amplifier, you can have stability problems when the output is loaded with capacitance. This could be solved by increasing the current of the output buffer and thereby the power consumption

 

[A.Anand Srinivasan]

a open loop amplifier would have many transistors in saturation and cutoff other than a few...