QXXXXXXX NC NB NE <NS> MNAME <AREA> <OFF> <IC=VBE,VCE>
Examples:
Q23 10 24 13 QMOD IC=0.6,5.0 Q50A 11 26 4 20 MOD1
NC, NB, and NE are the collector, base, and emitter nodes, respectively. NS is the (optional) substrate node. If unspecified, ground is used. MNAME is the model name, AREA is the area factor, and OFF indicates an (optional) initial condition on the device for the DC analysis. If the area factor is omitted, a value of 1.0 is assumed. The (optional) initial condition specification using IC=VBE,VCE is intended for use with the UIC option on the .TRAN statement, when a transient analysis is desired starting from other than the quiescent operating point. See the .IC statement.description for a better way to set transient initial conditions.
BJT Models (both NPN and PNP)
The bipolar junction transistor model in DR. 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 simpler Ebers-Moll model is used if the Gummel-Poon parameters are not specified. In either case, charge storage effects, ohmic resistances, and a current-dependent output conductance can be included if desired.
The DC model is defined by the parameters IS, BF, NF, ISE, IKF, and NE which determine the forward current gain characteristics, IS, BR, NR, ISC, IKR, and NC which determine the reverse 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 non-linear depletion layer capacitances which are determined 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, XTI. 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 following table. The parameter names were modified to be more easily understood by the program user, and to better reflect both physical and circuit design thinking. The parameter names used in SPICE2 also are accepted.
Modified Gummel-Poon BJT Model Parameters
Name Meaning Units Default Area
IS transport saturation current A 1.0E-16 *
BF ideal maximum forward beta - 100
NF forward current emission coefficient - 1.0
VAF forward early voltage V infinite
IKF corner for forward beta high current roll-offA infinite *
ISE B-E leakage saturation current A 0 *
NE B-E leakage emission coefficient - 1.5
BR ideal maximum reverse beta - 1
NR reverse current emission coefficient - 1
VAR reverse early voltage V infinite
IKR corner for reverse beta high current roll-offA infinite *
ISC B-C leakage saturation current A 0 *
NC B-C leakage emission coefficient - 2
NK high-current roll-off coefficient .5
ISS substrate junction saturation current A 0
NS substrate junction emission coefficient 1
RB zero bias base resistance W 0 *
IRB current where base res is half max value A infinite *
RBM minimum base resistance at high currents W RB *
RE emitter resistance W 0 *
RC collector resistance W 0 *
CJE B-E zero-bias depletion capacitance F 0 *
VJE B-E built-in potential V 0.75
MJE B-E junction exponential factor - 0.33
TF ideal forward transit time s 0
XTF coefficient for bias dependence of TF - 0
VTF voltage describing VBC dependence of TF V infinite
ITF high-current parameter for effect on TF A 0 *
PTF excess phase at freq=1.0/(TF*2p) Hz degrees 0
CJC B-C zero-bias depletion capacitance F 0 *
VJC B-C built-in potential V 0.75
MJC B-C junction exponential factor - 0.33
XCJC fraction of B-C depletion cap connected to - 1
internal base node
TR ideal reverse transit time s 0
CJS zero-bias collector-substrate capacitance F 0 *
QCO epitaxial region charge factor coulomb 0
RCO epitaxial region resistance W 0
VO carrier mobility knee voltage V 10
GAMMA epitaxial region doping factor 10p
VJS substrate junction built-in potential V 0.75
MJS substrate junction exponential factor - 0
XTB forward and reverse beta temp exponent - 0
EG energy gap for temperature effect on IS eV 1.11
XTI temperature exponent for effect on IS - 3
TRE1 RE temperature coefficient (linear) °C-1 0
TRE2 RE temperature coefficient (quadratic) °C-2 0
TRB1 RB temperature coefficient (linear) °C-1 0
TRB2 RB temperature coefficient (quadratic) °C-2 0
TRM1 RBM temperature coefficient (linear) °C-1 0
TRM2 RBM temperature coefficient (quadratic) °C-2 0
TRC1 RC temperature coefficient (linear) °C-1 0
TRC2 RC temperature coefficient (quadratic) °C-2 0
KF flicker-noise coefficient - 0
AF flicker-noise exponent - 1
FC coeff for forward-bias depletion cap formula - 0.5
* The parameter scales with area.