I am trying to design a circuit using a transistor but I don't understand the parameters of the transistor written in the program. Does anyone know what is the meaning of the following symbols?

I_s,B_R,R_B,R_E,T_R, M_JE, C_JC0, V_JC, B_F, V_A, R_C, T_F, C_JE0, V_JE, M_JC

I do understand the logic of a PNP and NPN transistor. I don't understand the names of the parameters here.


here is the figure from the editor:

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  • 1
    \$\begingroup\$ These are the common (and very few less common) parameters of the "usual" bipolar transistor model. So, the shortest possible answer to your question is a complete intro to the BJT… which has been done in every textbook on semiconductor components and really can only be done by reading a book. Hence, your question is too broad. \$\endgroup\$ Dec 20, 2017 at 12:46

2 Answers 2


These are model parameters. In a circuit simulator a model is used to simulate the behavior of a transistor. One of the simplest models is the Transistor diode model

More commonly used by circuit designers is the Hybrid Pi model, this is a linearized (small signal) model.

The list goes on, there are many models.

The model used by the simulator will be even more complex than both models mentioned above. Complex models need many parameters to "tune" the model such that it not only behaves as an NPN transistor but as a BC547 or 2n2222 or 2n3055 in particular. These are all NPNs but have very different maximum currents and beta (current gain) to name only two.

Some examples of model parameters: R_B: base series resistance R_C: collector series resistance C_JC0: Junction capacitance B_F: Foward mode current gain

See more here: Spice Model


I found the following here:

BJT Parameters

BF Forward active current gain

BR Reverse active current gain

IS Transport saturation current

CJE Base-emitter zero-bias junction capacitance

CJC Base-collector zero-bias Junction capacitance

VJE Base-emitter built-in potential

VJC Base-collector built-in potential

VAF Forward mode Early voltage

VAR Reverse mode Early voltage

NF Forward mode ideality factor

NR Reverse mode ideality factor

Thank you for the reply, it also helped me find the other parameters


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