Bipolar Transistors
Figure 3-1 illustrates the equivalent circuit for the npn bipolar junction transistor.
Figure 3-1: A circuit for the bipolar transistor.
The pnp transistor model is similar in all regards to the npn transistor, with the difference that the polarities of the currents and voltages involved are reversed. The following equations are used to compute the relations between currents and voltages in the circuit.
There are also two capacitances that use the same formula as the junction capacitance of the diode model. In the parameter names below, replace x with C for the base-collector capacitance and E for the base-emitter capacitance.
The model parameters are listed in the table below.
BF
BR
CJC
CJE
FC
IKF
IKR
IS
10-15 A/m2
ISC
ISE
MJC
MJE
NC
NE
NF
NR
RB
0 Ω⋅m2
RBM
0 Ω⋅m2
RC
0 Ω⋅m2
RE
0 Ω⋅m2
TNOM
VAF
VAR
VJC
VJE