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Beff parameter and saturation current

yefJ

Hello i have  created 25uA  current threw the nmos and pmos at gpdk45nm technology for the purpose of creating an opamp.

For NMOS in gate drain connection(saturation): W=120n L=1.2u 

After simulating i got the desired result of 24.9uA current. 

beff_nmos=22.7492u (mobility*Cox)

Vth_nmos=320.23m (threshold)

However when i tried to put it in the saturation current formula shown bellow it gives me a result 5 times lower then simulated.

Where did i go wrong interpreting the Model parameter table shown bellow?maybe i should take other parameter instead of Beff to get the fomula match the simulation?

Thanks

I_nmos=C_ox*mobility*0.5*(W/L)*(Vgs-Vt)^2=beff*0.5*(W/L)*(1.8-0.320)^2=22.74*10^-6*0.5((240*10^-9)/(1.2*10^-6))(1.8-0.320)^2=4.9809696 × 10^-6

NMOS:
Vth_nmos=320.23m (threshold)

PMOS parameters

Vt=-0.315

Parents

  • You're using a bsim4 model which has very different equations from the much simpler model equations you're trying to feed parameters which have a different meaning into. The model is much more complex, so trying to get an exact match is pretty pointless.

    The details of the bsim4 model can be found in the Spectre Circuit Simulator Components and Device Models Reference manual.

    Regards,

    Andrew.

Reply

  • You're using a bsim4 model which has very different equations from the much simpler model equations you're trying to feed parameters which have a different meaning into. The model is much more complex, so trying to get an exact match is pretty pointless.

    The details of the bsim4 model can be found in the Spectre Circuit Simulator Components and Device Models Reference manual.

    Regards,

    Andrew.

Children

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