DEPARTMENT OF ELECTRICAL ENGINEERING
Spice simulation of Transistors
All semiconductor devices are specified by using two command lines. The first statement defines the element and the second one is the model statement.
The syntax for the model statement is:
MODName is the name of the model for the device.. The Type refers to the type of device and can be any of the following:
The parameter values specify the device characteristics as explained below.
Qname C B E BJT_modelName
The bipolar transistor's name has to start with a Q
.MODEL BJT_modName NPN (BF=val IS=val VAF=val)
in which BF is the ß, IS is the saturation current and VAF is the Early voltage. If no values are specified, the default values are assumed (ß=100; IS=1e-16A, and VAF=infinite).
Mname D G S B ModName L= W=
The MOS transistor's name has to start with a M
.MODEL ModName NMOS (KP= VT0= lambda= gamma=)
in which KP=uCox. The default values are KP=20uA/V2; and the rest is equal to 0.
Example of a NPN Transistor Amplifier
Consider the circuit of the figure below. We are interested in finding the DC voltages and current, as well as the voltage gain and the input resistance seen by the input source.
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