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region of operation of mos transistor in CMOS circuits

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hemal

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hi,

can some one tell me in what region the mos transistors are operating in digital CMOS circuiits?

cutoff & linear ???

or

cutoff & saturation ???

--Hemal
 

for a digital design

consider a inverter:

input is high --> output is low --> pmos in cutoff, nmos in linear
input is low --> output is high --> pmos in linear , nmos in cutoff

at transition time transisitor goes to sat as well, but in stable condition its cutoff/linear
 

I ave got a question similar to above questio. I have read in book "Design of analog integrated CMOS integrated circuits" by Behzad Razavi that in order to work PMOS transistor as a switch in triode region, the following conditions must be true.
|Vgs|> |Vth|
|Vds|< |Vgs-Vth|
and Vd-Vg< |Vth|

I am not able to understand the last condition.. Can some body explain please..

thanks
 

The first 2 conditions are enough. The third one can be derived from the 2nd one. For example, in NMOS FET, the 2nd condition is
Vd - Vs < Vg - Vs - Vth => Vd - Vg < -Vth.
I don't know which page you got your equation from in the book. But you got the idea.
 
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