mos veff

For fix current:

1. higher current density?
2. larger device size lower current density?
3. higher Vgs less Vds?

how to test setup to fairly compare the linearity of a device?

For MOS devices:

At fixed bias current, decreasing W/L increases linearity. Simply because for a MOS differential pair decreasing the overdrive voltage (Veff) increases linearity. Note that to obtain the limit of this linearity, the bias points should be carefully adjusted to prevent, for example, turning off the tail current source.

Resistive oder inductive degeneration!

If the amp is in A-mode and have bias current I which component gives the most straight line as load curve between the maximum current 2*I and the maximum voltage.: "a resistor, or inductor at specific frequency"

The inductor is w/o noise