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102 2. Tutorial
Similarly, we define a simplified Ebers-Moll model for transistors operating in the forward active
region.
Both models are now stored in the global database:
In[11]:= Circuit[
Model[
Name −> NPNBJT,
Selector −> EbersMollForwardActive,
Scope −> Global,
Ports −> {C, B, E},
Parameters −> {betaf, Js, Area, Global[Temperature]},
Translation −>
{alphaf −> betaf/(1+betaf),
Is −> Js*Area, Vt :> ThermalVoltage[Temperature]},
Variables −>
{Current[B, C], Voltage[B, C],
Current[B, E], Voltage[B, E]},
Definition −>
Equations[
Current[B, C] == −Is*(Exp[Voltage[B, E]/Vt]),
Current[B, E] == Is/alphaf*(Exp[Voltage[B, E]/Vt])
]
]
] // ExpandSubcircuits;
In[12]:= GlobalSubcircuits[]
Out[12]=
NPNBJT, EbersMoll, NPNBJT, EbersMollForwardActive
2.6.6 Nonlinear DC Circuit Analysis
Calculating the Bias Point of a Transistor Circuit
Analog Insydes’ nonlinear modeling capabilities and numeric equation solver allow for solving
circuit analysis problems quickly and reliably without tedious and error-prone hand calculations.
Let’s demonstrate one such application:
Determine the operating-point currents and voltages IB, IC, VBE, VCE for the circuit shown in
Figure 6.6, if (a) RB ⩵ k and (b) RB ⩵ k. Assume that the transistor has an emitter area of
mil , Β f ⩵ , Β r ⩵ , J S ⩵ ΜAmil , and that it operates at a temperature of K. The
values of the supply voltage and the collector resistance are VCC ⩵ V and RC ⩵ k.