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[30 pts]How to determine regions of operation of

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mouzid

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How to determine regions of operation of MOS transistor

Could somebody tell me how to find the regions of operation of a NMOS (resp. PMOS) ? What is the procedure to follow and the circuit to simulate using Cadence tools ?

Any Lab/Tutorial to share ?
 

dedalus

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In schematic window press "Edit"-"Component Display...". In appeared window press "parameter" in "Select Label" section, press "operating point" and "DC" in "Parameter Labels" section. In the schematic window click on a transistor and return to the "Edit Component Display" window. Choose "vgs" (gate-source voltage), "vth" (threshold voltage), "vds" (drain-source voltage), "vdsat" (maximum drain-source voltage for which transistor operates in linear region).

After you run dc operating point simulation, in analog environment press "Results" - "Annotate" - "DC Operating Points", in the schematic window near transistor four labels will appear with values of vgs, vth, vds and vdsat.

If vgs > vth, transistor operates in strong inversion region.
If vgs < vth, transistor operates in weak inversion region.
If vgs > vth and vdsat < 78 mV (at T=27 C), transistor operates in moderate inversion region.
If vds > vdsat, transistor operates in active region.
If vds < vdsat, transistor operates in linear region.

Instead of these four parameters you can choose "region" parameter, but it returns numerical value and I don't know correspondence between those numbers and regions of operation.
 

erikl

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dedalus said:
Instead of these four parameters you can choose "region" parameter, but it returns numerical value and I don't know correspondence between those numbers and regions of operation.
See here (last posting from safwatonline).
 
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    mouzid

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mouzid

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Hi dedalus
dedalus said:
In schematic window press "Edit"-"Component Display...". In appeared window press "parameter" in "Select Label" section, press "operating point" and "DC" in "Parameter Labels" section.In the schematic window click on a transistor and return to the "Edit Component Display" window.

I did that and everythings were OK.

Choose "vgs" (gate-source voltage), "vth" (threshold voltage), "vds" (drain-source voltage), "vdsat" (maximum drain-source voltage for which transistor operates in linear region).
Here starts the problem. Attached are my windows before and after selecting one transistor of my circuit.

I cant select the vgs, vth... that you talked about.
 

dedalus

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I don't know what the problem is. But I've remembered another way to define region of operation. In Analog Environment press "Results" - "Circuit Conditions".
Using this tool you can annotate (with colored frame) all transistors in schematic which operate in specified region.
 

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