Hi Vivek,

100ns seems quite short for complete wake-up, but you may find some interesting ideas in the domain of switched op-amp circuits introduced by Crols and Steyaert (that's at least my earliest reference). In this technique, some switches in switched-capacitor circuits are moved inside the amplifier, which output is switched to high impedance in one clock period. It may be worth having a look at the following paper:
Switched-opamp: an approach to realize full CMOS switched-capacitor circuits at very low power supply voltages
Crols, J.; Steyaert, M.;
IEEE Journal of Solid-State Circuits
Volume 29,  Issue 8,  Aug. 1994 Page(s):936 - 942

Paul