Code history

Model history

Since the updates for SiMKit 3.1 (May 2008) the code history is included in the model history. Older code history can be found below.

Bipolar Model Mextram 504

Below is an overview of the relation between level and code versions.
The background of the compact model identification scheme can be read here.

Mextram 504 SiMKit
level.version.implementation code revision release date
504.10.1 1.378 4.0 2012-07-25
504.10.0 1.323.2.1 3.8 2012-02-02
504.9.1 1.309.2.1 3.7 2011-08-04
504.9.1 1.292.2.8 3.6 2011-01-18
504.9.0 1.273 3.5.2 2010-10-12
504.8.1 1.249 3.4 2009-12-17
504.8.0 1.243.2.3 3.3 2009-06-25
504.7.1 1.238 3.2 2008-12-02
504.7.0 1.232 3.1.2 2008-07-24
504.7.0 1.229.2.2 3.1 2008-05-21
504.6.5 1.214.2.1 3.0.3 2008-01-31
504.6.4 1.202 2.5 2007-04-30
504.6.3 1.193 2.4 2006-10-23
504.6.2 1.164 2.3 2006-03-16
504.6.1 1.144 2.2 2005-08-03
504.6.0 1.137 2.1.1 2005-04-11
504.5.0 1.116 2.0.1 2004-11-17
504.4.0 1.97 1.3 2004-04-20
504.3.1 1.80 1.2.1 2004-02-20
504.3.0 1.65 1.1.1 2003-10-27
504.2.2 1.35 1.0 2003-04-30
504.2.1 1.31 SMK/PMK 2002-09-25
504.2.0 1.26 SMK/PMK 2002-03-21
2012/02 Release of Mextram 504.10.1
 
  • The equilibrium state of the parasitic BCS transistor has been improved.
2012/02 Release of Mextram 504, 504.10.0
 
  • The parasitic current of the Base-Collector-Substrate transistor is now modeled. The model parameter EXSUB (Flag for extended modeling of substrate currents) has been added.
  • The approximate value of fT as presented by the operating point information showed suspect trends & values. The calculation has been modified. The updated value of the OP fT shows now good resemblance to the verilog-A version of Mextram 504.10 and to the fT calculated in an alternative way via two-port analysis.
  • The calculation of OP values Cb1b2 and Cb1b2x has been corrected, now they are identical to the values obtained with the verilog-A model.
2011/08 Release of Mextram 504, 504.9.1
  When the instance parameter MULT is set to zero, the model evaluation is done more efficiently.
2011/01 Release of Mextram 504, 504.9.1
 
  • Mextram 504 is implemented in a thread-safe way. This can lead to some minor changes in the results. The information about the linearization of exponentials in the diode currents (when converged) is less specific than before.
  • A new instance parameter PRINTSCALED has been added to this model. When PRINTSCALED is set to any value other than zero (the default) the model will print the scaled parameters of the model when the DC operating point information is printed.
2010/10 Release of Mextram 504, 504.9.0
 
  • Lower bound of parameter TVGEB is changed to zero.
  • Added to operating point information:
    • external terminal voltages VBE, VBC, VCE, VSE, VBS, VSC
    • external terminal currents IE, IS
  • The collector-substrate junction is now modeled by an ideal diode current.
    This model has a physics based temperature scaling with a mobility temperature scaling parameter ASUB. Parameters:
    • ICSS Collector-substrate ideal saturation current
    • ASUB Temperature coefficient for mobility of minorities in the substrate
  • The noise sources Ib3, Ib3fl, Iex and Iexfl and the noise sources XIex and XIexfl have been connected in the right places - this was overseen when the resistances RCblx and RCbli were introduced, in SiMKit 3.1.
2009/12 Release of Mextram 504, 504.8.1
 
  • Minor code changes.
2008/12 Release of Mextram 504, 504.8.0
 
  • Zener tunneling currents in the Emitter base junction model has been added to the Mextram model. Mextram 504 adopted a model of Zener tunneling current in the emitter-base junction. It describes the Zener tunneling current as it flows in the emitter-base junction when the junction is forced in reverse bias (VEB > 0). In Mextram, in the forward bias regime it is assumed that the Zener tunneling current can always be negelected. This is implemented by formally setting the value of the Zener tunneling current identically equal to zero in forward bias and gives the computational advantage that Zener current does not need to be evaluated in forward bias. The OP output of Mextram504 has been extended with Izteb: Zener tunneling current in the emitter base junction.
2008/12 Release of Mextram 504, 504.7.1
 
  • There was a difference in the SiMKit implementation of the emitter current through the resistor RCBLI with respect to the Verilog-A implementation of Mextram. This difference has been resolved.
  • Inconsistent behavior (between Pstar and Spectre) was seen in noise output when the parameter KAVL was set to 1. A change in the way negative correlated noise is handled in Spectre has resolved this problem.
  • Fixed for ADS: the SiMKit implementation of NFmin hardly depended on Vce for S-Parameter frequency analysis above 10GHz.
2005/04 Release of Mextram 504, 504.7.0
 
  • Introduction of the distributed parasitic collector resistance, which is needed for adequate ac-modeling, e.g. simultaneous modeling of cut-off frequency, bandwidth and unilateral power gain.
    Added model parameters:
    RCBLX: Resistance of Collector Buried Layer under the eXtrinsic transistor
    RCBLI: Resistance of Collector Buried Layer under the Intrinsic transistor
    Default values are RCBLX = 0 and RCBLI = 0, so the implementation is backwards compatible with previous implementations.
  • New operation point information has been added:
    Vb1c4: External base-collector bias with contact resistance RCBLI
    Vc3c4: External collector-collector bias over contact resistance RCBLX
    Vc4c1: Bias over intrinsic buried layer
    IRBC: Current through constant base resistance
    IRCC: Current through collector contact resistance
    IRCBLX: Current through extrinsic collector resistance
    RCBLX: Resistance of Collector Buried Layer under the eXtrinsic transistor
    RCBLI: Resistance of Collector Buried Layer under the Intrinsic transistor
  • Pdiss is formulated in terms of conductances GCBLX and GCBLI.
    These are set to zero in case the corresponding nodes vanish (so when RCBLX = 0 and RCBLI = 0).
  • The calculation of BnT_Bn has been made more robust.
  • A problem in the temperature scaling of the emitter-base diffusion voltage VDE,the collector-base diffusion voltage VDC, and the collector-substrate diffusionvoltage VDS in case of Tk = Trk has been corrected.
  • At high voltage values, an error in the derivatives could lead to convergence problems. The derivatives have been corrected.
2005/04 Release of Mextram 504, 504.6.0
 
  • Added parameter dAIs for fine tuning of temperature dependence of IsT
  • "GEM=0" added to equation of the avalanche current
  • Upper clipping value 1.0 of Kavl introduced
2004/10 Release of Mextram 504, 504.5.0
 
  • Addition of temperature dependence of the thermal resistance.
  • Addition of noise due to avalanche current.
2004/04 Release of Mextram 504, 504.4.0
  Noise of collector epilayer has been removed
2004/01 No model changes for Mextram 504.
  Release of Mextram 503, 504.5.0
 
  • Improved description of base and substrate currents
2003/10 Release of Mextram 504, 504.3.0
 
  • MULT has been moved in list of parameters
  • Lower clipping value of Tref changed to -273°C
  • Added IC, IB and ßdc to operating point information
2002/03 Release of Mextram 504, 504.2.0
  Changes in implementation for increased numerical stability
 
  • Numerical stability increased of xi/Wepi at small VC1C2
  • Numerical stability increased of p0*
2001/09 Release of Mextram 504, 504.1.0
 
  • Lower bound on Rth is now 0ºC/W
  • Small changes in Fex and QB1B2 to enhance robustness
2001/04 Release of Mextram 504, 504.0.0
  Small fixes:
 
  • Parameters Rth and Cth added to MULT-scaling
  • Expression for α in operating point information fixed
  Changes w.r.t. June 2000 version:
 
  • Addition of overlap capacitances CBEO and CBCO
  • Change in temperature scaling of diffusion voltages
  • Change in neutral base recombination current
  • Addition of numerical examples with self-heating
2000/06 Release of Mextram 504, 504.0.0(preliminary version)
 
  • Complete review of the model
1995/06 Release of Mextram 504, 503.2.0
 
  • Improved description of Early voltage
  • Improved description of cut-off frequency
  • Parameter compatible with level 503.1
1994/01 Release of Mextram 504, 503.1.0

Code history

Bipolar Model Mextram 504

The table below outlines the major changes to the file called "device_t504i.c", which can be found in the source code.

2008/01/31 Mextram 504.6.5.
  Code changes
 
  • New flexible topology architecture implemented
  • Small improvement in noise implementation for non-correlated noise sources
2007/04 Mextram 504.6.4 is identified in the code as revision 1.202. All code differences with the previous version (504.6.4) can be found in this diff file.
  Minor code changes
2006/10 Mextram 504.6.3, which is identified in the code as revision 1.193. All code differences with the previous version (504.6.2) can be found in this diff file.
  Implemented model changes
 
  • Several convergence problems have been solved.
  • The derivatives used in the calculations of the model have been made more robust.
  • The temperature derivatives have been made robust.
  • The lower clip value of BRI has been changed from 1e-4 to 1e-10.
  • Performance of temperature scaling has been improved.
  • To improve convergence in the model, the self-heating effect is included in the explosion voltage for the spectre part of the model. The explosion voltage is updated and not constant anymore. The implemented code was suggested by cadence to improve convergence, however, the temperature derivatives of the explosion voltage are not taken into account.
  • A gmin convergence aid has been implemented. This makes the convergence more robust. The results are not always only positive but also in some cases the convergence may be slower. The gmin convergence aid implementation has been made common to all simulators.
  • The performance of self-heating models has been improved by reducing the time spent in clipping.
  Minor code changes
 
  • There was a warning regarding specifying the working region when using spectre -h <model name>. This warning is removed.
  • In the past an unclear warning was given when the effective length and/or effective width of a transistor were clipped. This warning has been made more specific.
2006/03 Mextram 504.6.2, which is identified in the code as revision 1.164. All code differences with the previous version (504.6.1) can be found in this diff file.
  Implemented model changes
  None
  Other code changes
  Minor code changes
2005/08 Mextram 504.6.1, which is identified in the code as revision 1.144. All code differences with the previous version (504.6.0) can be found in this diff file.
  Implemented model changes
  None
  Other code changes
  Minor code changes
2005/04 Mextram 504.6.0, which is identified in the code as revision 1.137. All code differences with the previous version (504.5.0) can be found in this diff file.
 
  • Added parameter dAIs for fine tuning of temperature dependence of IsT
  • "GEM=0" added to equation of the avalanche current Iavl
  • Upper clipping value 1.0 of Kavl introduced
  Other code changes
 
  • Division by almost zero solved by changing the calculation of Iavl
  • Division by zero fixed when the substrate current Iqs becomes zero
  • An overflow protected version of exp() is now used to calculate some variables.
  • Scaling rule for saturation current has been changed.
  • Implementation of temperature limiting for self-heating
2004/11 Mextram 504.5.0, which is identified in the code as revision 1.116.
  All code differences with the previous version (504.4.0) can be found in this diff file.
 
  • Addition of temperature dependence of the thermal resistance, Ath.
  • Addition of noise due to avalanche current.
  Other code changes
 
  • Convergence problems due to Vdt<0 (temperature increase due to self-heating) solved
 
  • A bug fixed in the implementation of the self-heating models as a result of which clipping is being done.
 
  • Improvement in simulation time
 
  • The message 'No DC path from node 'tn' to ground, Gmin installed to provide path', displayed when the thermal terminal of the self-heating model is not connected, has been removed
2004/04 Mextram 504.4.0, which is identified in the code as revision 1.97.
  All code differences with the previous version (504.3.1) can be found in this diff file.
  Implemented model changes
 
  • Noise of collector epilayer has been removed
  Other code changes
 
  • Speed improvements
  • Numeric instability solved
  • Bug fix for dissipation in the PNP transistor.
2004/02 Mextram 504.3.1, which is identified in the code as revision 1.80.
  All code differences with the previous version (504.3.0) can be found in this diff file.
  Implemented model changes
 
  • None
  Other code changes
 
  • A bug fixed in the implementation of the collector base overlap capacitance (QBEO).
  • Derivatives of qBI implemented
2003/10 Mextram 504.3.0, identified in the code as revision 1.65. The code differences will not be given in a diff file, because a complete new set up is made since the last version on the web.
  Implemented model changes
 
  • Addition of extra operation point information:Ic, Ib and BetaDC.
  Other code changes
 
  • A small bug fixed in the implementation of the noise model
  • Added clipping for exmod, exphi and exavl.
  • Solved problem in calculation of operation point information Cbe and Cbc.
  • Solved problem with the noise in RCV
  A substrate version of Mextram, "bjt504" and "bjt504t", and a version without substrate of Mextram, "bjtd504" and "bjtd504t", are implemented in SiMKit.
2003/04 Mextram 504.2.2, which is identified in the code as revision 1.35
  All code differences with the previous version (504.2.2) can be found in this diff file.
  Implemented model changes
 
  • None
  Other code changes
 
  • Derivation by zero in the calculation of rcv_factor solved
  • Derivation by zero in the calculation of EP_OPO_fT solved
  • Matrix stamping is changed for using residu as RHS
2002/09 Mextram 504.2.1, which is identified in the code as revision 1.31
  All code differences with the previous version (504.2.0) can be found in this diff file.
  Implemented model changes
 
  • None
  Other code changes
 
  • MULT scaling of the parameters CBEO and CBCO
  • Fixed error in the derivative dEW_dXiWepi
  • Fixed error in the derivative dQts_dVT
  • Fixed error in CJC_ratio_DVT
  • Fixed error in IP_VFC_DVT
  • Derivatives dIB2C2_dVT and dIB2C1_dVT are removed
  • The absolute value of RHS(BR_PTH) is now used
  • The lower bound for qBI is removed
2002/03 Mextram 504.2.0, which is identified in the code as revision 1.26
  ll Code Differences With The Previous Version (504.1.0, known as Pstar 4.2 p011214) can be found in this diff file.
  Implemented model changes
 
  • See release 504.2 in the model history above
  Other code changes
 
  • Addition of source code numbering
  • Change in the way noise output is generated
  • Some minor changes in derivative of yi (Reported by Analog Devices)
  • Fixed error in droot_dVT and in calculation of Gem (Reported by Analog Devices)
  • Removed some double calculations in selfheating part of: WD, Vtc, Ec, Qtex (Reported by Analog Devices);
  • Made sure that the values of OUTVAR(BR_RCC/RE/RBC) are of the most recent iteration when used with self-heating (Reported by Analog Devices);
  • Typo in BR_QBC(O) and BR_QBE(O) fixed (Reported by Analog Devices);
  • CJC_ratio_DVT partly fixed (Reported by Analog Devices);
  • IP_Bn_DVT fixed (Reported by Analog Devices); and
  • Sign of vb2c2star as needed in Pdiss changed for PNP's.

Known bugs

Mextram 504.3.1 (2004/02/15) has the following known bugs (These will be fixed in the next version of the code that will be released).

  • There is a problem with RTH=0 which is not yet completely solved. There is currently no short cut, but the voltage over the VT branch is 1e-38.

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