Hi Chong,

the technology does not represent a limitation on low power, but on speed. The higher supply in "older" technologies is favorable for low power analog design. On the other hand, if you limit your supply voltage to 1.2V, you lose this advantage and the higher threshold voltages in 0.5 compared to more recent technologies will make your circuit harder to design. You must differentiate "low-power" from "low-voltage". Some people tend to mix these parameters because they are related for digital circuits.

What you must basically do for low-voltage design is to limit the number of stacked devices. The telescopic amplifier is an example of what you should not do for low-voltage design.

The Ph.D. by A.Abo at Berkeley may give you some info on low-voltage design:
http://kabuki.eecs.berkeley.edu/~abo/abothesis.pdf
Some more links on low-voltage design:
http://www.elec.ucl.ac.be/enseignement/ELEC2650/chapter4.pdf
http://www.elec.ucl.ac.be/enseignement/ELEC2650/chapter5.pdf

For low-voltage amplifiers, you can also look for papers written by Steyaert or Vittoz.

Good luck

Paul