I/O transistor vs Analog transistor

Could I/O transistor be used to build circuits? What's the difference between I/O transistor and analog one.

jimway said:

Could I/O transistor be used to build circuits? What's the difference between I/O transistor and analog one.

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hi,
i think there is no obviously difference between them,but that, the i/o circuits may have some thick oxide gate,or higher voltage devices for level shift.besides, for esd issues, the layout of some transistors are considered carefully .

that's my viewpoints.
jeff

I havn't put it clearly.
The following comments are shown in the bsim model file:
hints : measurements and parameter fitting in the voltage range:
*
* |vds| = 0 ... 2.5 (+10%) v : analog mode
* |vds| = 0 ... 3.3 (+10%) v : io mode
* |vgs| = 0 ... 2.5 (+10%) v : analog mode
* |vgs| = 0 ... 3.3 (+10%) v : io mode
* |vbs| = 0 ... 2.2 v

Accually these two modes are used to describe the same mosfet.
Could this transistor be used to achieve circuits with the 3.3v voltage supply?

jfyan's answer is correct. Normaly there is a thicker gate oxide for I/O devices since they see 3.3V [and here I/O also can mean analog I/O as well as digital I/O].

In your case since Vds and Vgs is defined for the same transistor I can only suggest that when they say analog they mean transistors are mostly in saturation region [Vds >= (Vgs-Vt)] where life time of transistors shorter due to high fields between Drain and Source and resulting impact ionization degradation. For I/O (here means digital I/O only) transistors are used as switches and passes through saturation region only very short time during switching (low duty cycle) so the life time of transistor shortens much less and transistors can be used at higher 3.3V with reasonable life time (Provided that gate breakdown allows it to operate 3.3V).

there is no difference except io transistors need some layout improvment

Technique improvement.

I/O transistor is primary for I/O drive capability.
Analog transisor care about GM/high gain.

Advanced process does provide high gain I/O transistor for analog circuit design.

In layout design, the I/O transisitor must be carefully designed, especially in the region of drain

It should be the ESD difference! The I/O mos will have the ESD protection!

There is no difference of spice model.
But some manufacture request lager IO MOS transistor length for ESD.
Also there are alot of different design rule in the layout side.