The bipolar junction transistor model in SPICE is an adaptation of the integral charge control model of Gummel and Poon. This modified Gummel-Poon model extends the original model to include several effects at high bias levels. The model automatically simplifies to the simpler Ebers-Moll model when certain parameters are not specified.


Parameter Description Default
Model Specify a BJT model (NPN/PNP) or subcircuit name. The remaining parameters are only used if a model is specified. If a subcircuit is used, make sure the order of the nodes in the subcircuit matches that of a BJT (Collector, Base, Emitter). If not, use the PINS parameter to specify the correct order.  
AREA The area factor determines the number of equivalent parallel devices of a specified model. The affected parameters are marked with an asterisk under the heading 'area' in the model descriptions. This parameter is optional. 1
OFF Set to OFF to set terminal voltages to zero during operating point analysis. Can be useful as an aid in convergence. If a device is specified OFF, the dc operating point is determined with the terminal voltages for that device set to zero. After convergence is obtained, the program continues to iterate to obtain the exact value for the terminal voltages. If a circuit has more than one dc stable state, the OFF option can be used to force the solution to correspond to a desired state. If a device is specified OFF when in reality the device is conducting, the program still obtains the correct solution (assuming the solutions converge) but more iterations are required since the program must independently converge to two separate solutions. This parameter is optional.  
IC Assigns initial voltages to the junctions (VBE, VCE) in transient analysis. Note that the initial conditions apply only if the UIC (Use Initial Condition) option is enabled in the Transient Analysis dialog box. This parameter is optional.  
TEMP Specifies the temperature at which the component operates. This value, if specified, takes precedence over the analysis temperature. This parameter is optional.