Why does voltage gain of fixed bias transistors not as same I calculated ?

WBahn

Joined Mar 31, 2012
30,078
So BF is max value of beta right?
It's the maximum ideal forward beta, but it is NOT the maximum beta of the transistor. The SPICE models use a curve fit to determine the beta as a function of collector current and there are a number of other parameters that go into it, such as ISE, IKF, NE, and NK. There are tools that you can use to enter data points from the data sheet and it will return the values of the model parameters that reasonably approximate the entered data. The resulting maximum beta may is usually larger than BF.

Here's some detail you might find interesting:

https://www.youspice.com/spice-modeling-of-a-bjt-from-datasheet/5/

Page 1 has a listing of the parameters and a brief description for a particular level of the SPICE BJT transistor model.
 

Thread Starter

Heroz

Joined May 29, 2022
31
It's the maximum ideal forward beta, but it is NOT the maximum beta of the transistor. The SPICE models use a curve fit to determine the beta as a function of collector current and there are a number of other parameters that go into it, such as ISE, IKF, NE, and NK. There are tools that you can use to enter data points from the data sheet and it will return the values of the model parameters that reasonably approximate the entered data. The resulting maximum beta may is usually larger than BF.

Here's some detail you might find interesting:

https://www.youspice.com/spice-modeling-of-a-bjt-from-datasheet/5/

Page 1 has a listing of the parameters and a brief description for a particular level of the SPICE BJT transistor model.
Thank you.
 
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