Go to www.awrcorp.com
Back to search page Click to download printable version of this guide.

(Obsolete) Mextram 504 (Nonlinear BJT Model): MXTR504N



This element is OBSOLETE and is replaced by the Mextram 504 BJT Model (MXTR504) element. Mextram 504 is Philips' most recent vertical bipolar transistor model. Compared to Mextram 503, this model has improved descriptions of transistor characteristics and easier parameter extraction. The improved transistor characteristics are achieved by changing some of the model's formulations. The resulting equations are much smoother, such that first-order and higher derivatives are better. The complete set of equations and derivation are found in references [1] and [2], respectively. Parameter extraction is improved by decreasing parameter interdependence, without losing the physical basis of the model. As a result, the number of parameters has increased from 62 to 71.

MXTR504N is a full implementation of Philips' Mextram 504 model. It includes self-heating, which adds complexity to the model and increases the computation time. Due to the model's improved smoothness, tests show that MXTR504, with self-heating disabled, converges in general better than MXTR503.

Equivalent Circuit


Name Description Unit Type Default
ID Element ID   MX1
*NPN NPN (flag, information only)   1
*PNP PNP (flag, information only)   0
*LEVEL Release (Information only)   504
*EXMOD Flag for extended modeling of reverse current gain   1.0
*EXPHI Flag for distributed high frequency effects in transient simulations   1
*EXAVL Flag for extended modeling of avalanche currents   0.0
*IS Collector-to-emitter saturation current Amperes 5e-017A
*BF Forward current gain   215
*XIBI Fraction of ideal base current from sidewall   0.0
*IBF Saturation current of the non-ideal forward base current Amperes 2e-14A
*VER Reverse Early voltage Voltage 2.5V
*VEF Forward Early voltage Voltage 44V
*MLF Non-ideality factor of the non-ideal forward base current   2
*VLF Cross-over voltage of the non-ideal forward base current Voltage 0.5V
*IK High-injection knee current Amperes 15.0e-3A
*BRI Ideal reverse current gain   7
*IBR Saturation current of the non-ideal base current Amperes 1e-12
*VLR Cross-over voltage of the non-ideal reverse base current Voltage 0.2
*XEXT Parameter dependency of VBC1   0.63
*WAVL Epilayer thickness used in weak-avalanche model   1.1
*VAVL Voltage determining curvature of avalanche current Voltage 3V
*QBO Base charge at zero bias   1.2e12
*ETA Factor of the built-in field base)   4.0
*AVL Weak avalanche parameter   50.0
*EFI Electric field intercept   0.7
*IHC Critical current for hot carriers Amperes 4
*AXI Smoothness parameter for the onset of quasi-saturation   0.3
*RCC Constant part of the collector resistance Resistance 25.0 ohm
*RCV Resistance of the unmodulated epilayer Resistance 150
*SCRCV Space charge resistance of the epilayer Resistance 1250
*SFH Current spreading factor epilayer Resistance 0.6 ohm
*RBC Constant part of the base resistance Resistance 23
*RBV Variable part of the base resistance at zero bias Resistance 18
*RE Emitter series resistance Resistance 2.0 ohm
*TAUNE Minimum delay time of neutral and emitter charge Conductance 0.3e-9s
*MTAU Non-ideality factor of the neutral and emitter charge   1.18
*TAUE Minimum transit time of stored emitter charge Time 0.002ns
*TAUB Transit time of stored base charge Time 0.0042ns
*TEPI Transit time of stored epilayer charge Time 0.041ns
*TAUR Transit time of reverse extrinsic stored base charge Time 0.52ns
*CJE Zero bias BE depletion capacitance Faraday 0.25e-12F
*VDE BE built-in voltage Voltage 0.9V
*PE BE grading coefficient   0.33
*XCJE Reaction of BE capacitance to the sidewall   0.5
*CBE0 Emitter-base overlap capacitance   0
*CJC Zero bias BC depletion capacitance Faraday 0.13e-12F
*VDC BC built-in voltage Voltage 0.6V
*PC BC grading coefficient   0.4
*XP Constant part of CJC   0.2
*MC Collector current modulation coefficient   0.5
*XCJC Fraction of BE capacitance under emitter   0.1
*CBC0 Collector-base overlap capacitance   0
*TNOM Reference (extraction) temperature Celsius 25oC
*TEMP Ambient (baseplate) temperature Celsius 25oC
*VGE Emitter Bandgap Voltage 1.01V
*VGB Base Bandgap Voltage 1.18V
*VGC Collector Bandgap Voltage 1.205V
*VGJ EB Bandgap Voltage 1.1V
*VI Ionization voltage base dope Voltage 0.4V
*NA Maximum base dope (per cm^3)   3e17
*ER VLF and VLR temp coefficient   0.002
*DEG Bandgap difference over the base   0
*XREC Pr-factor of the recombination part of IB1   0
*AQB0 Temperature coefficient of the zero bias base charge   0.3
*AE Temperature coefficient of the resistivity of the emitter   0
*AB Base resistance temp coefficient   1.35
*AEPI Epilayer temp coefficient   2.15
*AEX Extrinsic base temp coefficient   1.0
*AC Buried layer temp coefficient   4.0
*DVGBF Band-gap voltage difference of forward current gain Voltage 0.05V
*DVGBR Band-gap voltage difference of reverse current gain Voltage 0.045V
*DVGTE Band-gap voltage difference of emitter stored charge Voltage 0.05V
*KF Base current 1/f noise   2e-6
*KFN Nonideal base 1/f noise   2e-6
*AF 1/f noise exponent   1.0
*ISS base-substrate saturation current Amperes 6.0e-16A
*IKS Knee current of the substrate Amperes 0.005e-3A
*CJS Zero-voltage substrate capacitance Faraday 1.0e-12F
*VDS CS built-in voltage Voltage 0.5V
*PS CS grading coefficient   0.33
*RTH Thermal resistance   300
*CTH Thermal capacitance   3e-9
*VGS Substrate Bandgap Voltage V
*AS =AC for closed buried layer; =AEPI for open buried layer.   2.15
*NFLAG Noise flag; 1=ON, 0=OFF    
*MULT Number of devices in parallel   1

* indicates a secondary parameter

Parameter Details

Parameter default values correspond to HSPICE default values and correspond to those listed as test parameters in Philips' documentation [1].

Parameter Restrictions and Recommendations

The range of many of the model parameters is restricted. In spite of extensive error-trapping in the Cadence® AWR® Microwave Office® software implementation, some parameter errors may not be trapped. See [1] for details on such restrictions.

Implementation Details

This model is mapped into HSPICE as a NPN G-device with parameters LEVEL and VERS set to 6 and 504, respectively. The complete set of equations is too complex to be listed here. Consult the references for specific information. Ref. [1] defines the model in detail and ref. [2] contains the derivation of the model.

Recommendations for Use

Like Mextram 503, Mextram 504 is an advanced model and should be used only where the need for accuracy justifies its complexity, and where parameter libraries are available. Care must be exercised when self-heating is enabled.


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.


[1] http://www.semiconductors.philips.com/acrobat/other/philipsmodels/b504.pdf

[2] http://www-us.semiconductors.philips.com/acrobat/other/philipsmodels/newsflash/nlur2002806.pdf:

Legal and Trademark Notice