Calculate of power mosfet on resistance

[nice2cu]

Hello,

I tried to calculate the Rds_on of a power mosfet. I can get the tox, uo, and vtho from the model file (BSIM4). By using tox, cox can be calculated by cox=ε0*εox/tox.

The on resistance of a power mosfet in linear region is given by

Rds_on=1/(µ0*cox*(W/L)*(vgs-vth0)).

The problem here is that the calculated value is always half of the simulated one when I tried different W/L.

I checked the model parameter µ and vth, they are very close to the value I used in hand calculation.

Please help me to understand what's wrong here. Thanks!!

Eric

 

[mfding]

I am not sure if the equations are correct for practical devices (especially short channel ones). But check the source and drain contact resistant. Are they comparable to the channel resistance give by these equations?

Hello,

I tried to calculate the Rds_on of a power mosfet. I can get the tox, uo, and vtho from the model file (BSIM4). By using tox, cox can be calculated by cox=ε0*εox/tox.

The on resistance of a power mosfet in linear region is given by

Rds_on=1/(µ0*cox*(W/L)*(vgs-vth0)).

The problem here is that the calculated value is always half of the simulated one when I tried different W/L.

I checked the model parameter µ and vth, they are very close to the value I used in hand calculation.

Please help me to understand what's wrong here. Thanks!!

Eric

 

[erikl]

I checked the model parameter µ and vth, they are very close to the value I used in hand calculation.

Are you sure you use the same tox?