gain mismatch from practial and theoritical

[Esakki raja]

How to check the theoretical value and practical value for gain in cs stage ?

theoretical value ----> As per our calculation from formula

practical value ---->As per our simulation from the tools

Is there any impact occur for these two values?

 

[crutschow]

I don't really understand you question. :?: Certainly there is likely to be a difference between the theoretical value and simulated value with the amount of difference depending upon the completeness of the calculations and the accuracy of the models.

 

[FvM]

A simulation result is also a theoretical value, based on formulas used in the simulator model.

What you probably mean is the difference between the simple quadratic model assumed in the first MOSFET chapter of a text book and the complexer models used by the simulator.

A practical value would refer to a real measurement in my view.

 

[Esakki raja]

Hi
i explain my doubt. that is if we are using the cs amplifier with current source load, the gain Av = -gm1(ro1||ro2) this formula used to find the gain in theoretical . But it is not same for the simulator value from the waveform in practical.

 

[FvM]

Is the frequency suffiently low to ignore any device capacitances?
How did you derive gm, and ro?
Are you sure that the simulator uses the same transistor parameters as applied in the gm and r0 calculation?
Do you know which MOSFET model level is selected?
Is the simulation working in small signal range?
Did you read Razavi Chapter 16 Short Channel Effects and Device Models?

 

[Esakki raja]

I had taken the gm in the dc operating point results from simulation and r0 taken from (ro1||ro2) .Is there any effects are considered for the gm and r0 calculation and which book has detailed about that?