take a unit bias current which is usually generated from a bandgap, then use this current to generate all the bias currents and bias voltages.Always look in terms of bias currents and not voltages.When i say this i mean, try to flow a particular value of current which you intend and then keep scaling the size to achieve minimum overdrive.
i agree with amarnath.... that is what is usually done in CMOS circuits.... it is where we can bias a circuit to a particular region of operation using current....
I'll try and post whatever i can on ota circuits....