L7Part1_PSpice Gummel-Poon Model of BJT L6_1

# L7Part1_PSpice Gummel-Poon Model of BJT L6_1 - PSpice...

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PSpice Gummel-Poon BJT Model Equations Lecture 7 Part 1 Monday Jan. 25, 2010 Zubair Rehman

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2 BJT Models (Both NPN and PNP) 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 will automatically simplify to the simpler Ebers- Moll model when certain parameters are not specified. The parameter names used in the modified Gummel-Poon model have been chosen to be more easily understood by the program user, and to reflect better both physical and circuit design thinking. The dc model is defined by the parameters IS, BF, NF, ISE, IKF, and NE which determine the forward current gain characteristics, and VAF and VAR which determine the output conductance for forward and reverse regions. Three ohmic resistances RB, RC, and RE are included, where RB can be high current dependent. Base charge storage is modeled by forward and reverse transit times, TF and TR, the forward transit time TF being bias dependent if desired, and nonlinear depletion layer capacitances which are determine by CJE, VJE , and MJE for the B-E junction. CJC, VJC, and MJC for the B-C junction and CJS, VJS, and MJS for the C-S (Collector-Substrate) junction. The temperature dependence of the saturation current, IS, is determined by the energy-gap, EG, and the saturation current temperature exponent, XTL. Additionally base current temperature dependence is modeled by the beta temperature exponent XTB in the new model. The BJT parameters used in the modified Gummel-Poon model are listed in the next few slides. The parameter names are used in earlier versions of SPICE2 are still accepted.
3 Modified Gummel-Poon BJT Parameters

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4 Modified Gummel-Poon BJT Parameters (cont’d)
5 Modified Gummel-Poon BJT Parameters (cont’d)

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6 So that the beginning user need specify only a few model parameters and program control parameters and program control Parameters to effect a simulation. Simulation results are available either as tabular listings of the output variables or as line printer plots. The program contains 8000 Fortran IV statements, and requires 40,000 decimal words of core memory to execute of the CDC 6400 available at the University of California, Berkley. * The basic program organization is shown in Figure 1. The circuit is described on a set of punched cards. The program first reads and processes the input deck and checks for input errors. The next step in the simulation is establishing the necessary set of pointers for the sparse matrix routines [7]. These pointers enable the two dimensional Y matrix to be collapsed into a one dimensional vector containing only the nonzero Y-matrix terms. The matrix routines then operate only on the nonzero terms contained in this vector. This saves a substantial amount of core memory and central processor execution time. The next step in the simulation is the actual analysis.
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L7Part1_PSpice Gummel-Poon Model of BJT L6_1 - PSpice...

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