Difference between gm/id method and Vov design method

[dkdlek93]

I want to know the difference between gm/id and Vov method when designing amplifier.
And why use the gm/id method.

As far as I know, there are three aspects.
1. Available for low power designs.
2. Gm, id, L, and w of input Mosfet pair can be found more systematically at specified power and speed performance.
3. Use gm/id because it is difficult to model with Vov when using mosfet in a weak inversion area.

Am I right?
Also, I would appreciate it if anyone could tell me why people use the gm/id method.

 

[Dominik Przyborowski]

If you have a map between given parameter nad bias point you can use whatever you want, as long as your base is a physical model. If your model is loussy than no matter which method you will use - both gives your wrong results.

 

[martinnl]

I think one important aspect, perhaps not as important as the other mentioned but still, is that the gm/Id method is more direct. Both gm and Id directly describe something in the circuit compared to Vov which in itself doesn't really say much.