This is a further development of the well known Angelov/Zirath/Rorsman, or Chalmers, model. It is especially good for use with HEMT devices, but is also useful for MESFETs. Angelov2 includes improved capacitance and breakdown modeling, as well as modeling of thermal effects.
Although this model is similar in many ways to the original Angelov model, it is not identical, and, in general, parameters for the earlier model cannot be used in this one.
Parameter | Description | Units | Default Value |
---|---|---|---|
ID | Device ID | Text | AF1 |
*IPK | Current at peak Gm | ma | 50 |
*P1 | I/V polynomial coefficient | 1.0 | |
*P2 | I/V polynomial coefficient | 0 | |
*P3 | I/V polynomial coefficient | 0 | |
*P4 | I/V polynomial coefficient | 0 | |
*P5 | I/V polynomial coefficient | 0 | |
*P6 | I/V polynomial coefficient | 0 | |
*B1 | P1 term | 0 | |
*B2 | P1 term | 3.0 | |
*VPKS | Gate voltage at peak Gm in sat | Voltage | -0.2 V |
*VPK0 | Gate voltage at peak Gm near 0 Vds | -0.4 V | |
*ALPHR | Drain I/V knee parameter | 2.0 | |
*ALPHS | Drain I/V knee parameter at saturation | 0 | |
*LAMBDA | Drain-source resistance parameter | 0 | |
*LAMSB | Surface breakdown parameter | 0 | |
*VTR | Threshold voltage for breakdown | Voltage | 5.0 |
*VSB2 | Surface breakdown parameter | 0.0 | |
*TAU | Gate-drain time delay | Time | 0 |
*CGS0 | Gate-source capacitance parameter | Capacitance | 0 |
*CGSP | Linear part of Cgs | Capacitance | 0 |
*PC10 | Gate-source capacitance polynomial coef. | 0 | |
*PC11 | Gate-source capacitance polynomial coef. | 1.0 | |
*PC110 | Polynomial coef. to model peaked Cgs | 0 | |
*PC111 | Polynomial coef. to model peaked Cgs | 0 | |
*ADIV | Term to model peaked Cgs (1= no peaking) | 1 | |
*PC20 | Gate-source capacitance polynomial coef. | 0 | |
*PC21 | Gate-source capacitance polynomial coef. | 0.5 | |
*CGD0 | Gate-drain capacitance parameter | Capacitance | 0 |
*CGDP | Linear part of Cgd | Capacitance | 0 |
*PC30 | Gate-drain capacitance polynomial coef. | 0 | |
*PC31 | Gate-drain capacitance polynomial coef. | 0.5 | |
*PC40 | Gate-drain capacitance polynomial coef. | 0 | |
*PC41 | Gate-drain capacitance polynomial coef. | 1.0 | |
*CDS0 | Fixed drain-source capacitance (not scaled) | Capacitance | 0 |
*CDSW | Scalable drain-source capacitance | Capacitance | 0 |
*CPG | Gate-pad parasitic capacitance (not scaled) | Capacitance | 0 |
*CPD | Drain-pad parasitic capacitance (not scaled) | Capacitance | 0 |
*ISG | Gate diode current parameter | Current | 10^{-20} A |
*NG | Gate diode ideality factor | 1.0 | |
*RG | Gate resistance | Resistance | 1.0 ω |
*RS | Source resistance | Resistance | 1.0 ω |
*RI | Intrinsic resistance | Resistance | 1.0 ω |
*RD | Drain resistance | Resistance | 1.0 ω |
*RGD | Gate-drain resistance | Resistance | 1.0 ω |
*RCW | RF drain-source resistance parameter | Resistance | 300 ω |
*CRF | Capacitance that determines Rds break frequency | Capacitance | 10^{-6} F |
*LS | Source inductance (not scaled) | Inductance | 0.0 |
*LG | Gate inductance (not scaled) | Inductance | 0.0 |
*LD | Drain inductance (not scaled) | Inductance | 0.0 |
*RTH | Thermal resistance C/W | 0.1 | |
*TEX | Temperature at which parameters were extracted | Temperature | 25 C |
*TEMP | Baseplate temperature | Temperature | 25 C |
*TAU_TH | Thermal time constant | Time | 1 mS |
*TCIPK | Thermal IDS IPK coefficient | 0 | |
*TCP1 | Thermal IDS P1 coefficient | 0 | |
*TCCGS0 | Thermal CGS0 coefficient | 0 | |
*TCCGD0 | Thermal CGD0 coefficient | 0 | |
*TCRCW | Thermal RCW coefficient | 0 | |
*TCCRF | Thermal CRF coefficient | ||
*DTMAX | Maximum temperature increase (C) in self-heating | ||
*TMIN | Minimum device temperature | ||
AFAC | Gate-width scale factor | 1.0 | |
NFING | Number of fingers scale factor | 1.0 |
* indicates a secondary parameter
This is a further development of the well known Angelov/Zirath/Rorsman, or Chalmers, model. It is especially good for use with HEMT devices, but is also useful for MESFETs. Angelov2 includes improved capacitance and breakdown modeling, as well as modeling of thermal effects.
Although this model is similar in many ways to the original Angelov model, it is not identical, and, in general, parameters for the earlier model cannot be used in this one.
The drain current is given by
where
and
Many of the above parameters are related directly to the peak current and transconductance of the device. See the references for the original Angelov model for further information.
The model uses a capacitance formulation to determine the reactive gate-to-source and gate-to-drain currents. This approach allows the model to be consistent with time-domain (SPICE) formulations. In this implementation, the gate charge is formulated as a single function of gate and drain voltages, so the gate current is
The first term in the above equation represents gate-to-source current, and the second, gate-to-drain current. This approach simplifies parameter extraction, because no transcapacitances are needed and the charge derivatives are identical to the small-signal capacitance.
The resulting capacitance functions are given by the following expressions:
and
The parameter ADIV is used to account for a peak and decrease in capacitance, with increasing gate bias voltage, that sometimes is observed in pHEMTs. In most cases, ADIV = 1 and the expressions are symmetrical. It is important to recognize that this capacitance formulation is entirely different from the original Angelov model, and the parameters of the original model are not transferable to this one.
The model uses a simple approach to account for nonlinear, frequency-sensitive drain-to-source resistance, often called drain dispersion. The drain-to-source resistance is described by a current source having the following I/V characteristic:
where
is given by (2). The parameter RCW, which has units of resistance, is only approximately the drain-to-source resistance in current saturation; it is best viewed as a model parameter used to fit the measured small-signal drain-source resistance.
This element has a large inductor in parallel to provide a return for dc currents generated in the element and to force its dc voltage to be zero under all conditions.
The thermal model modifies the parameters IPK, P1, CGS0, CGD0, RCW, and CRF as follows:
where
and T is the instantaneous temperature, determined from an electrothermal equivalent circuit. The electrothermal circuit consists of a thermal resistance and capacitance. The total power dissipation in the device, not just the drain dissipation, is used to determine temperature. The temperature coefficients are chosen so that, in most cases, they will be positive quantities; however, occasionally one or more may be negative.
RCW and CRF. The temperature dependence of RCW and CRF requires some explanation. In general, RCW (the RF drain-to-source resistance) decreases with temperature so, for accurate power-amplifier analysis, its temperature dependence should be included. Although CRF is a nonphysical component, it models the transition between the DC and RF drain-to-source resistance regions. This transition increases in frequency as temperature increases, so CRF should be made temperature dependent when necessary to model this phenomenon. In circuits where there are no frequency components near the transition frequency (which is usually on the order of 1 KHz to 1 MHz), this phenomenon need not be modeled, so TCCRF can be set to zero.
The temperature increase, ΔT, is calculated from an electrothermal equivalent circuit consisting of a thermal resistance, RTH, and a capacitance, C. C is calculated from the thermal time constant, TAU_TH. = RTH AzA C. ΔT is limited to 300 C in a numerically acceptable manner. The power used to calculate ΔT includes all RF and DC power dissipated in the device, not just the drain dissipation.
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.
There are no references for this model. This model was implemented before publishing. The above information comes from personal communication from Prof. Angelov. The breakdown modeling is a joint effort of I. Angelov and S. Maas.
For further information about the model, contact Cadence AWR Technical Support.