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Cutoff, Triode and Saturation

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ccw27

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triode saturation

In order to conclude whether the transistor is off or not we should check whether Vg<Vth rather than Vgs<Vth, is that right? Otherwise a wrong conclusion may result.

Also can someone point what does each "region" correspond to in dc operating point parameter. Like region=1≡cutoff,region=2≡saturation and region=2≡triode. Is that right?

Thanks
 

approximation vgs-vth vgs linear triode region

Cotoff - open circuit infinite resistance if Vgs<Vt

Saturation - voltage controlled resistence - high
Triode - voltage controlled resistance - lower
 

threshold voltage triode saturation

Vg < Vth is not corrected. Should be check Vgs < Vth.

Also in BSIM parameters, 0=cutoff, 1=triode, 2 = saturation, 3=sub-threshold, 4=breakdown if I remember right.....
 

triode cut-off

ccw27 said:
In order to conclude whether the transistor is off or not we should check whether Vg<Vth rather than Vgs<Vth, is that right? Otherwise a wrong conclusion may result.

Also can someone point what does each "region" correspond to in dc operating point parameter. Like region=1≡cutoff,region=2≡saturation and region=2≡triode. Is that right?

Thanks
Click to expand...


In section 2 of Razavi's book,'design of cmos ana IC', give you a detailed explain of the mos's three region.
 

saturation triode

by definition, saturation --> Vgs > Vth AND Vds > Vgs - Vth.

as for numbers representing mode of operation in OP simulation:

0 --> Off
1 --> linear/triode
2 --> Saturation

Adios
 

saturation cutoff triode

Vgs is the most important value for the mosfet.
 

regions of transistor triode off 0 1 2 3 4

So if vgs is a little less than vth and vds>vdsat, that corresponds to subthreshold region? What is the typical margin for "little less than"? Also what model you use to size your transistor in subthreshold?

Thanks
 

saturation and triode region vth<vg

Vgs>Vth is just an approximation of not being cutoff region. Vgs must be greater than Vth at least 50 mV to ensure it is in not cutoff region. Actually if Vgs just little greater or smaller than Vth, the device will enter sub-threshold region.

Furthermore, in complex model such as BSIM3 or 4, the boundary between every regions become very blurred, and usually appeared in continuously.
 

triode operating point

the relation of Vgs,Vth&Vds
 

transistor cutoff saturation triode

see the Vds and vdsat to distinguish the saturation and triode
 

cutoff triode

Does anyone know any good reference on subthreshold design?

Thanks
 

triode and saturation region

you are right
but 3 is tride
in spice
 

cut off saturation points

VGS is rather a correct measure because, the gate voltage relative to the source voltage
is what decides the inversion of the channel region, and not the absolute volatge of the
gate itself.....
 

triode subthreshold saturation

Cutoff : VGS<Vt VGD<Vt
Active: VGS>=Vt VGD<Vt
or VGS<Vt VGD>=Vt
Triode: VGS>=Vt VGD>=Vt

cited from Analysis and Design of Analog IC by Gray
 

cut off saturation

chinito said:
by definition, saturation --> Vgs > Vth AND Vds > Vgs - Vth.

as for numbers representing mode of operation in OP simulation:

0 --> Off
1 --> linear/triode
2 --> Saturation

Adios
Click to expand...

Where can I see these numbers?? in output file?? if so, as i understood now, i can know from the SPICE output file the state of each MOSFET in the circuit.. am I right? how?? please show me an example or a snap shot or what ever as i was looking for this issue long time ago.
Note that i am using BSIM level 7 model..

Thanks in advance,
Ahmad
 

is there triode operation in subthreshold region

cutoff : Vgs > Vth of course Vg>Vth is not right
Vgs > Vth AND Vds > Vgs - Vth sarution
 

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