two stage opamp (W and L)

[yihsiu]

could someone tell me how to decide and calculate W / L?
the voltage is from 13 to -13


1. to assume the Iref current (but i don't know how much should i assume)
2 to find the K=µ Cox and Cox= εox/ tox ()
3. how can i calculate the value of the caps?

thanks

 

[yihsiu]

sorry i forget something
how can i find the Vt , K, εi in those two documents

thanks a lot

 

[elbadry]

The threshold voltage is the parameter named Vtho in the documents.
The Mobility is the parameter named U0.

Note that this is the threshold voltage with the source and bulk shorted. If you have stacked transistors and your technology is not a twin-well technology then this wil change (substrate effect).

As for the design, I think that you should first specify some current budget (i.e. how much current can you use in the whole circuit) then allocate each block the appropriate amount of current dpending on the requred gain and functionality.


How to determine the current depends on the required gain-size-swing and dissipation. gain=gm*Ro in general. So, to increase gain you have to increase either gm or Ro or both.increasing gm can be done by increasing current or by simply increasing the W/L ratio; however caution has to be taken for the increased input capacitance. Ro can be increased by increasing the transistors length or by cascoding or both....

whta i want to say is that there are many choices/tradeoffs. The choice of topology and current are totaaly dpendent on your application.