This element is OBSOLETE and is replaced by the UCSD HBT Model (HBT) element with the EXT_FLAG parameter set to "Disabled". The UCSD HBT model, like the Berkeley BSIM3 model, is designed as an "industry standard" SPICE model. Its basic concepts are the same as the Gummel-Poon BJT model; capacitances are a combination of diffusion and depletion components, for example, but the expressions are more complex. This model includes breakdown and self-heating.
Documentation for this model is available in print[1].
Name | Description | Unit Type | Default |
---|---|---|---|
ID | Element ID | UH#1 | |
SELFT | Flag; 0=no self-heating (T=TOP); 1=self-heating is included | 0 | |
BKDN | Flag; 0=no breakdown; 1=breakdown is included | 0 | |
TBP | Base-plate temperature | Temperature | 26.85 C |
TNOM | Temperature at which model parameters were extracted | Temperature | 26.85 C |
TOP | Best-guess operating temperature | Temperature | 26.85 C |
IS | Saturation current | Current | 10^{-22} |
NF | Forward ideality factor | 1.0 | |
NR | Reverse ideality factor | 1.0 | |
ISA | Collector EB barrier limiting current | Current | 10^{13} |
NA | Collector EB barrier ideality factor | 2.0 | |
ISB | Collector BC barrier limiting current | Current | 10^{13} |
NB | Collector BC barrier ideality factor | 2.0 | |
VAF | Forward early voltage | Voltage | 1000.0 |
VAR | Reverse early voltage | Voltage | 1000.0 |
IK | Forward current knee | Current | 10^{13} |
BF | Forward ideal current gain | 10^{4} | |
BR | Reverse ideal current gain | 10^{4} | |
ISE | Saturation value for nonideal forward base current | Current | 10^{-27} |
NE | Ideality factor for nonideal forward base current | 2.0 | |
ISEX | Saturation current for emitter leakage diode | Current | 10^{-27} |
NEX | Ideality factor for emitter leakage diode | 2.0 | |
ISC | Saturation value for intrinsic BC current | Current | 10^{-27} |
NC | Ideality factor for intrinsic BC current | 2.0 | |
ISCX | Saturation current for extrinsic BC junction current | Current | 10^{-27} |
NCX | Ideality factor for extrinsic BC junction current | 2.0 | |
FA | Factor to specify avalanche voltage | 0.9 | |
BVC | C-B breakdown voltage (BVcb0); positive | Voltage | 1000.0 |
NBC | Exponent for BC multiplication factor vs. voltage | 8.0 | |
ICS | Saturation value for collector-substrate current | Current | 10^{-27} |
NCS | Ideality factor for collector-substrate current | 2.0 | |
RE | Emitter resistance | Resistance | 0.001 |
REX | Extrinsic emitter leakage diode series resistance | Resistance | 0.001 |
RBX | Extrinsic base resistance | Resistance | 0.001 |
RBI | Intrinsic base resistance | Resistance | 0.001 |
RCX | Extrinsic collector resistance | Resistance | 0.001 |
RCI | Intrinsic collector resistance | Resistance | 0.001 |
CJE | BE depletion capacitance at zero voltage | Capacitance | 2e-8 |
VJE | BE built-in potential | Voltage | 1.6 |
MJE | BE capacitance exponent (0.1<MJE<0.9) | 0.33 | |
CEMIN | Min value of intrinsic BC capacitance | Capacitance | 1e-8 |
FCE | Factor for BE capacitance approximation near Vbi | 0.8 | |
CJC | BC depletion capacitance at zero voltage | Capacitance | 2e-8 |
VJC | BC built-in potential | Voltage | 1.4 |
MJC | BC capacitance exponent (0.1<MJC<0.9) | 0.33 | |
CCMIN | Min value of intrinsic BC capacitance | Capacitance | 1e-8 |
FC | Factor for BC capacitance approximation near Vbi | 0.8 | |
CJCX | Extrinsic BC capacitance at zero voltage | Capacitance | 2e-8 |
VJCX | Extrinsic BC capacitance Vbi | Voltage | 1.4 |
MJCX | Extrinsic BC capacitance exponent (0.1<MJCX<0.9) | 0.33 | |
CXMIN | Minimum extrinsic BC capacitance | Capacitance | 1e-8 |
XCJC | Factor for partitioning BC capacitance | 1.0 | |
CJS | Substrate depletion capacitance at zero voltage | Capacitance | 0.0 |
VJS | Built-in potential for substrate capacitance | Voltage | 1.4 |
MJS | Substrate capacitance exponent (0.1<MJS<0.9) | 0.5 | |
TFB | Base transit time | Time | 0.0 |
TBEXS | Excess BE transit time | Time | 0.0 |
TBCXS | Excess BC transit time | Time | 0.0 |
TFC0 | Collector forward transit time | Time | 0.0 |
ICRIT0 | Critical current for junction capacitance | Current | 1000000 |
ITC | Characteristic current for TFC | Current | 0.0 |
ITC2 | Characteristic current for TFC | Current | 0.0 |
VTC | Characteristic voltage for TFC | Current | 1000.0 |
TKRK | Forward transit time for Kirk effect | Time | 0.0 |
VKRK | Characteristic voltage for Kirk effect | Voltage | 1000.0 |
IKRK | Characteristic current for Kirk effect | Current | 1000000 |
TR | Reverse storage time for intrinsic BC diode | Time | 0.0 |
TRX | Reverse storage time for extrinsic BC diode | Time | 0.0 |
FEX | Excess phase factor | 0.0 | |
RTH | Thermal resistance | Resistance | 10^{-8} |
CTH | Thermal capacitance | Capacitance | 1e6 |
KFN | BE flicker noise constant | 0.0 | |
AFN | BE flicker noise exponent for current | 1.0 | |
BFN | BE flicker noise exponent for frequency | 1.0 | |
XTI | Exponent for IS temperature dependence | 2.0 | |
XTB | Exponent for beta temperature dependence | 2.0 | |
TNE | Coefficient for NE temperature dependence | 0.0 | |
TNC | Coefficient for NC temperature dependence | 0.0 | |
TNEX | Coefficient for NEX temperature dependence | 0.0 | |
EG | Activation energy for IS temperature dependence | 1.5 | |
EAA | Activation energy for ISA temperature dependence | 0.0 | |
EAB | Activation energy for ISB temperature dependence | 0.0 | |
EAE | Activation energy for ISE temperature dependence | 0.0 | |
EAC | Activation energy for ISC temperature dependence | 0.0 | |
EAX | Activation energy for ISEX temperature dependence | 0.0 | |
XRE | Coefficient for RE temperature dependence | 0.0 | |
XREX | Coefficient for REX temperature dependence | 0.0 | |
XRB | Coefficient for RB temperature dependence | 0.0 | |
XRC | Coefficient for RC temperature dependence | 0.0 | |
TVJE | Coefficient for VJE temperature dependence | 0.0 | |
TVJCX | Coefficient for VJCX temperature dependence | 0.0 | |
TVJC | Coefficient for VJC temperature dependence | 0.0 | |
TVJS | Coefficient for VJS temperature dependence | 0.0 | |
XTITC | Coefficient for ITC temperature dependence | 0.0 | |
XTITC2 | Coefficient for ITC2 temperature dependence | 0.0 | |
XTTF | Coefficient for TF temperature dependence | 0.0 | |
XTTKRK | Coefficient for TKRK temperature dependence | 0.0 | |
XTVKRK | Coefficient for VKRK temperature dependence | 0.0 | |
XTIKRK | Coefficient for IKRK temperature dependence | 0.0 | |
XRT | Coefficient for RTH temperature dependence | 0.0 | |
DTMAX | Maximum temperature rise above heatsink in Celsius degrees | Temperature | 1000.0 C |
AFAC | Area scale factor | 1.0 |
DTMAX. A temperature limit used to avert numerical difficulties in the self-heating model. The Cadence® AWR® Microwave Office® implementation also includes a minimum temperature fixed at 100 K (-173 C). You cannot change the minimum temperature.
TOP and TBP. The estimated device temperature is not listed in the tables in [1] because, in SPICE, the global temperature parameter is used for this quantity. In AWR Microwave Office software, however, TOP is included in the model's parameter list, and therefore can be different from the temperature of other parts of the circuit. TOP is your best estimate of device temperature in operation. It is used for parameters that depend on temperature only weakly, or have only a minor effect in the model. Including self-heating for such parameters increases the computational overhead of the model, for very little improvement in accuracy. TOP is essentially the same as the temperature parameter in conventional SPICE models, which employ thermal scaling but not self-heating.
TBP is the baseplate temperature, which you specify. [1] indicates that you should set this value by applying a voltage to a fifth, thermal node in the HBT. AWR Microwave Office software does not use this approach, because treating it as a model parameter is simpler and less error-prone.
CJx and CxMIN. Defaults have been changed to 2·10^{-20} F for the parameters CJE, CJC, and CJCX; and to 1*10^{-20} F for the parameters CEMIN, CCMIN, and CXMIN. The default values of zero, listed in [1], cause divide-by-zero errors.
HB_UCSD contains terms of the form (CJx/CxMIN)(1/MJx), where MJx is typically in the range of 0.33 to 0.50. With incorrect values for these parameters, it is easy to "crash" such equations. These errors are very difficult to trap without restricting the use of reasonable parameter values, so you should be aware of this problem and choose parameter values accordingly.
RTH and CTH. HBT_UCSD provides for a nonlinear thermal resistance, RTH, which is a function of temperature. This formulation makes the temperature increase, normally the dependent quantity, a function of itself. This could lead to numerical problems, poor convergence, instability, or other unusual behavior. Although AWR Microwave Office software attempts to make its models conform to the defining documentation (so SPICE and AWR Microwave Office calculations give the same results), in this case, AWR Microwave Office software makes RTH a function of TOP, instead of instantaneous device temperature.
BF and BR. The default values of BF and BR (10^{4}) specified in [1] present little problem in most practical cases, but if the base is biased with a current source (as might happen in the initial stages of a design), and BF/BR use the default values, bad convergence and strange results are possible. You should be careful to set these parameters to reasonable values, or make certain that BE leakage currents account for base current correctly.
If you exceed the following parameter limits, the parameter is modified as necessary to prevent a numerical error. In general, physically reasonable values are always acceptable.
CEMIN > 0.01 CJE.
CCMIN > 0.01 CJC.
0.1 < MJx < 0.9, where MJx is any of the parameters beginning with MJ.
FC and FCE must be in the range (0.001, 0.999). If either is outside this range, it is set to 0.5.
0.01 < FA < 0.99.
Device temperature must be greater than 100 K (-173 C).
HBT_UCSD includes collector-to-base breakdown and self-heating effects. You should exercise caution in making use of these effects. Breakdown is a strong nonlinearity which can cause convergence difficulties in a harmonic-balance simulator. Reference [1] warns that breakdown modeling can cause poor convergence even in time-domain simulators, and [2] gives some of the reasons. Self-heating also can introduce negative-resistance effects that cause difficult conversion in harmonic-balance simulation.
You can easily switch these effects on and off with the BKDN and SELFT flag parameters. If SELFT=0, the device temperature is set to TOP, and unless TOP=TNOM, thermal scaling is still performed.
Scaling is relatively simple:
All charges are scaled in proportion to AFAC;
All resistors are scaled inversely with AFAC;
All currents are scaled in proportion to AFAC.
The model equations are too extensive to include here. See reference [1] for further information.
This element does not have an assigned layout cell. You can assign artwork cells to any element. See “Assigning Artwork Cells to Layout of Schematic Elements” for details.