# Difference between regular and IO mosfet?

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#### allanvv

If I'm designing a low requirement (in both speed and accuracy) switched cap circuit and comparator for something like 45nm, should I use 1V transistors or the 3.3V IO ones? Power consumption isn't important, but area is. If I have a 5u/0.5u transistor, which will have better characteristics? My guess is that the 3.3V ones will be better for analog, especially from the increased headroom, but is the only downside that it's slower?

edit: I compared gpdk045's nmos1 and nmos2, which are 1.1V and 1.8V. Surprisingly, the 1.1V transistor had a better gm*ro, but the 1.8V transistor had double the ro. This is with a fixed Vgs = 0.5V for both of them, while Vds was scaled for each of them to 1.1V and 1.8V. W/L = 5u/0.5u. https://i.imgur.com/HCvmR.png

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