AnalogDE wrote on Jun 10th, 2008, 12:10am:You want to check to see that your Vds > Vdsat (for short channel transistors you want to look at the Vdsat given by SPICE, it's not equal to Vgs-Vt).
The worst case corner for headroom is
low VDD
slow corner (slow corner => transistors weaker => higher Vdsat req'd to keep in saturation)
highest temperature (high temp => lower mobility => higher Vdsat req'd)
and w/ transistors operating at their highest current levels (higher current => more Vdsat).
Let me add:
Slow corner for transistors!!
But
fast corner for resistors!!
Wether high or low temperature corner is worst-case depends on current densitity. For low current
usually the lowT corner is much more critical.
Bye Stephan