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(Obsolete) Mextram 503 NPN BJT Model: MXTR503N



There is no replacement for this OBSOLETE element. The Mextram model was developed as a general-purpose BJT model for use throughout the electronics industry. Mextram was developed at Philips, and the Cadence® AWR® Microwave Office® software model is a full implementation of Philips' Mextram 503 model. Mextram models a large variety of effects that are not included in the SPICE Gummel-Poon model; these include weak avalanche effects, hard- and quasi-saturation, hot-carrier effects in the epilayer, and substrate current. It includes improved temperature scaling, but not self-heating.

Equivalent Circuit


Name Description Unit Type Default
ID Element ID   MX1
*NPN NPN (flag, information only)   1
*PNP PNP (flag, information only)   0
*Release Release (information only)   503
EXMOD Flag for extended modeling of reverse current gain   1.0
*EXPHI (Not implemented)   0.0
EXAVL Flag for extended modeling of avalanche currents   0.0
*IS Collector-to-emitter saturation current Amperes 5e-14
*BF Forward current gain   140.0
*XIBI Fraction of ideal base current from sidewall   0.0
*IBF Saturation current of the non-ideal forward base current Amperes 2e-14A
*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   16.0
*IBR Saturation current of the non-ideal base current Amperes 8e-15A
*VLR Cross-over voltage of the non-ideal reverse base current Voltage 0.5V
*XEXT Parameter dependency of VBC1   0.5
*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 A 3.0e-3
*RCC Constant part of the collector resistance Resistance 25.0 ohm
*RCV Resistance of the unmodulated epilayer Resistance 750.0 ohm
*SCRCV Space charge resistance of the epilayer Resistance 1000.0 ohm
*SFH Current spreading factor epilayer Resistance 0.6 ohm
*RBC Constant part of the base resistance Resistance 50.0 ohm
*RBV Variable part of the base resistance at zero bias Resistance 100.0 ohm
*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
*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
*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
*TREF Reference (extraction) temperature Celsius 25oC
*DTA Device temperature rise above ambient in degrees C Celsius 0.0oC
*TAMB 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
*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   0.4
*KF Base current 1/f noise   2e-16
*KFN Nonideal base 1/f noise   2e-16
*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
*VGS Substrate Bandgap Voltage 1.15V
*AS =AC for closed buried layer; =AEPI for open buried layer.   2.15
*NFLAG Noise flag; 1=ON, 0=OFF   0
MULT Number of devices in parallel   1

* indicates a secondary parameter

Parameter Details

Parameter default values are those given in Philips' documentation [2] and are generally respected throughout the user community. Those defaults, however, are representative of RF or Microwave devices.

Parameter Restrictions and Recommendations

The range of many of the model parameters is restricted. In spite of extensive error-trapping in the AWR Microwave Office implementation, it is possible that some parameter errors may not be trapped. See [2] 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 503, respectively. The complete set of equations is too complex to be listed here. The user should consult the references for specific information. Ref. [1] contains technical background information and theory of the model, and the documents available from Philips' web site [2] define the model in detail.


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.

Recommendations for Use

Mextram is an advanced model. It should be used only where the need for accuracy justifies its complexity, and where parameter libraries are available. The Gummel-Poon model, GBJT, is recommended for simple applications.


[1] H. C. de Graaf and F. M. Klaassen, Compact Transistor Modelling for Circuit Design, Springer-Verlag, Vienna, 1990.

[2] Philips Semiconductor web site, http://www.semiconductors.com/Philips_Models/documentation/mextram

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