The Anholt HBT model is a modification of the well known Gummel-Poon model. Although it uses a similar topology, its expressions for temperature effects and transit time are very different. The model includes self-heating and accounts for nonreciprocal behavior.
Name | Description | Unit Type | Default |
---|---|---|---|
ID | Device ID | Text | HA1 |
*ISF | Forward saturation current | Current | 1e-13 |
*ISR | Reverse saturation current | Current | 1e-13 |
*BF | Forward current gain | 100.0 | |
*NF | Forward ideality factor | 1.0 | |
*VAF | Forward early voltage | Voltage | 1.0x10^{9} |
*IKF | Forward current knee | Current | 1e12 |
*ISE | BE leakage current param | Current | 0.0 |
*NE | BE leakage ideality factor | 1.5 | |
*BR | Reverse current gain | 1.0 | |
*NR | Reverse ideality factor | 1.0 | |
*VAR | Reverse early voltage | Voltage | 1.0x10^{9} |
*IKR | Reverse current knee | Current | 10e12 |
*ISC | BC leakage current param | Current | 0.0 |
*NC | BC leakage ideality factor | 2.0 | |
*CJE | CJ0 for BE junction | Capacitance | 0.0 |
*VJE | BE built-in voltage | Voltage | 0.75 |
*MJE | BE capacitance exponent | 0.50 | |
*TB0 | Constant part of the base transit time | Time | 0.0 |
*TB1 | Variable part of the base transit time | Time | 0.0 |
*NTB | Exponent for the base transit time | 5.0 | |
*TC0 | Collector transit time | Time | 0.0 |
*BVS | Saturation velocity parameter for TC | 1.0x10^{9} | |
*ITF | High-current parameter for the transit time | 0.0 | |
*PTF | Excess phase param; must be in degrees | Degrees | 0.0 |
*CJC | CJ0 for BC junction | Capacitance | 0.0 |
*VJC | BC built-in voltage | Voltage | 0.75 |
*MJC | BC capacitance exponent | 0.50 | |
XCJC | Fraction of Cbc connected to the internal node | 1.0 | |
TR | Reverse transit time | Time | 0.0 |
*CJS | CJ0 for substrate capacitance | Capacitance | 0.0 |
*VJS | Built-in voltage of the substrate capacitance | Voltage | 0.75 |
*MJS | Substrate capacitance exponent | 0.50 | |
*RB | Base resistance | Resistance | 0.01 |
*RB2 | Extrinsic base resistance | Resistance | 0.01 |
*RE1 | Emitter resistance | Resistance | 0.01 |
*RC2 | Collector resistance | Resistance | 0.01 |
*CBE | Extrinsic BE capacitance | Capacitance | 0.0 |
*CBC | Extrinsic BC capacitance | Capacitance | 0.0 |
*CCE | Extrinsic CE capacitance | Capacitance | 0.0 |
*LB | Base inductance (not scaled) | Inductance | 0.0 |
*LE | Emitter inductance (not scaled) | Inductance | 0.0 |
*LC | Collector inductance (not scaled) | Inductance | 0.0 |
*FC | Linearization term for forward-bias depletion capacitance | 0.5 | |
*ISS | Collector-substrate current param | Current | 0.0 |
*NS | Collector-substrate ideality factor | 1.0 | |
*TS | Collector-substrate diode storage time | Time | 0.0 |
*TNOM | Temperature at which parameters were extracted | Temperature | 26.85 |
*TBP | Baseplate temperature | Temperature | 26.85 |
*XTI | Temperature exponent for diode currents | 0.0 | |
*ABF | BF temperature coefficient | 0.0 | |
*ABR | BR temperature coefficient | 0.0 | |
*ANF | NF temperature coefficient | 0.0 | |
*ANR | NR temperature coefficient | 0.0 | |
*ANE | NE temperature coefficient | 0.0 | |
*ANC | NC temperature coefficient | 0.0 | |
*ANS | NS temperature coefficient | 0.0 | |
*VSF | Barrier height for ISF thermal modeling | Voltage | 0.0 |
*VSR | Barrier height for ISR thermal modeling | Voltage | 0.0 |
*VSE | Barrier height for ISE thermal modeling | Voltage | 0.0 |
*VSC | Barrier height for ISC thermal modeling | Voltage | 0.0 |
*VSS | Barrier height for ISS thermal modeling | Voltage | 0.0 |
*ARB | RB temperature coefficient | 0.0 | |
*ARB2 | RB2 temperature coefficient | 0.0 | |
*ARE | RE temperature coefficient | 0.0 | |
*ARE1 | RE1 temperature coefficient | 0.0 | |
*ARC2 | RC2 temperature coefficient | 0.0 | |
*ACJE | CJE temperature coefficient | 0.0 | |
*ACJC | CJC temperature coefficient | 0.0 | |
*AVJE | VJE temperature coefficient | 0.0 | |
*AVJC | VJC temperature coefficient | 0.0 | |
*ATB0 | TB0 temperature coefficient | 0.0 | |
*ATB1 | TB1 temperature coefficient | 0.0 | |
*ATC0 | TB1 temperature coefficient | 0.0 | |
*AITF | ITF temperature coefficient | 0.0 | |
*RTH | Thermal resistance | Capacitance | 0.001 |
*CTH | Thermal capacitance | Capacitance | 1.0 |
*AFAC | Area scale factor | 1.0 |
* indicates a secondary parameter
Certain parameters (especially IKF, IKR, VAF, and VAR) are seldom needed in HBTs. These are included to allow the model to be used for conventional BJTs as well as HBTs. It is essential to note that including such parameters does not necessarily make the model equivalent to the SPICE Gummel-Poon model.
Default parameter values for this model may not be the same as those of the SPICE Gummel-Poon model (GBJT). Be sure to be aware of differences when porting existing Gummel-Poon model parameters to this model.
Be careful specifying temperature coefficients. It is possible to create nonphysical parameters if they are too great. This is especially true of the NF, NE, NR, and NC parameters.
Resistances, capacitances, and currents are scaled in the usual manner: all resistors are scaled as 1/AFAC; junction currents and all capacitors are scaled in proportion to AFAC. Inductances LB, LE, and LC are not scaled.
The model is fundamentally the same as the Gummel-Poon model used in SPICE, with the addition of allowance for nonreciprocal behavior, self-heating, and a new expression for transit time as a function of collector voltage and current. The model also includes common extensions over the expressions in the references.
The collector current expression in the Gummel-Poon model has been modified to allow for nonreciprocal behavior of HBT devices. The SPICE parameter IS has been replaced by two parameters, ISF and ISR, that describe forward and reverse conduction, respectively. The current expression is
Q_{b} is the normalized base charge, as used in the Gummel-Poon model; q is electron charge, K is Boltzmann's constant, and T is temperature in Kelvin degrees. Note that T varies with power dissipation in the device. ISF and ISR are also functions of temperature (see below).
The expression for transit time is
(When V_{bc} > VJC, the square-root term in is corrected in the same manner as similar terms in depletion capacitances; the method is identical to the one used in SPICE.) The base-to-emitter diffusion charge is
Reverse diffusion charge is included in the model; it is part of the "inner" base-to-collector capacitance. In reverse operation, the transit time is simply TR.
The PTF parameter is an awkward way of specifying a simple time delay in the base-to-emitter voltage. PTF is defined as in the SPICE Gummel-Poon model. It must be given in degrees; then, the delay represented by this quantity is
Saturation currents (ISF, ISR, ISE, ISC, ISS) are scaled as follows:
where ISX is one of the parameters above, and VSX is the corresponding voltage parameter.
Other parameters are scaled as
where P is any of the thermally scaled parameters and AP is the corresponding temperature coefficient. (Be careful using this capability; see Note 3, above.) T is the instantaneous temperature, which includes effects of self-heating.
The model uses a conventional electrothermal self-heating model. RTH is the thermal resistance in degrees C per watt of power dissipation. CTH is the thermal capacitance, defined as
where t_{TH} is the thermal time constant of the device. CTH should never be set to zero; otherwise, the device temperature T cycles at the RF frequency. When the time constant is long compared to a period of the excitation waveform, the device temperature T is
The power dissipation, P_{diss}, includes all power dissipated in the device: DC sources at both the base and collector, as well as RF dissipation.
To prevent numerical difficulties, the device temperature, T, is limited to values greater than 100 K. An abrupt limit at 100 K would introduce convergence difficulties; therefore, the limiting function smooths the temperature in the vicinity of 100 K. This smoothing function introduces a small error throughout the entire temperature range; the maximum error, which occurs at 100 K, is approximately 7 K. Above 200K, the error is less than 0.5 K.
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.