non-physical parameter values permitted

[gjcoram]

It is non-physical to allow negative values for:

• saturation currents JSS, JSSWS, JSSWGS, JTSS, JTSSWS, JTSSWGS, JSD, JSSWD, JSSWGD, JTDS, JTSSWD, JTSSWGD
• capacitances CJS, CJSWS, CJSWGS, CJD, CJSWD, CJSWGD
• built-in potentials PBS, PBSWS, PBSWGS, PBD, PBSWD, PBSWGD

Also, I think the "info" attributes for PBS, etc. are incorrect (they look to match the info for CJS, etc.).

parameter real JSS = 0.0E-09 from (-inf:inf) ATTR(info="AREA COMPONENT OF CURRENT FOR JUNCTION DIODE, SOURCE SIDE (ASYMMETRICAL MODEL)"); parameter real JSSWS = 0.0E-12 from (-inf:inf) ATTR(info="SIDEWAYS COMPONENT OF CURRENT FOR JUNCTION DIODE, SOURCE SIDE (ASYMMETRICAL MODEL)");
parameter real JSSWGS = 0.0E-12 from (-inf:inf) `ATTR(info="GATE-SIDE COMPONENT OF CURRENT FOR JUNCTION DIODE, SOURCE SIDE (ASYMMETRICAL MODEL)");

parameter real JTSS = 0.0E-09 from (-inf:inf) ATTR(info="AREA COMPONENT OF TRAP-ASSISTED CURRENT FOR JUNCTION DIODE, SOURCE SIDE (ASYMMETRICAL MODEL)"); parameter real JTSSWS = 0.0E-12 from (-inf:inf) ATTR(info="SIDEWAYS COMPONENT OF TRAP-ASSISTED CURRENT FOR JUNCTION DIODE, SOURCE SIDE (ASYMMETRICAL MODEL)");
parameter real JTSSWGS = 0.0E-12 from (-inf:inf) `ATTR(info="GATESIDE COMPONENT OF TRAP-ASSISTED CURRENT FOR JUNCTION DIODE, SOURCE SIDE (ASYMMETRICAL MODEL)");

parameter real CJS = 0.0E-06 from (-inf:inf) ATTR(info="AREA COMPONENT OF CAPACITANCE FOR JUNCTION DIODE, SOURCE SIDE (ASYMMETRICAL MODEL)"); parameter real CJSWS = 0.0E-09 from (-inf:inf) ATTR(info="SIDEWAYS COMPONENT OF CAPACITANCE FOR JUNCTION DIODE, SOURCE SIDE (ASYMMETRICAL MODEL)");
parameter real CJSWGS = 0.0E-09 from (-inf:inf) `ATTR(info="GATESIDE COMPONENT OF CAPACITANCE FOR JUNCTION DIODE, SOURCE SIDE (ASYMMETRICAL MODEL)");

parameter real PBS = 0.800 from (-inf:inf) ATTR(info="AREA PARAMETER OF CAPACITANCE FOR JUNCTION DIODE, SOURCE SIDE (ASYMMETRICAL MODEL)"); parameter real PBSWS = 0.600 from (-inf:inf) ATTR(info="SIDEWAYS PARAMETER OF CAPACITANCE FOR JUNCTION DIODE, SOURCE SIDE (ASYMMETRICAL MODEL)");
parameter real PBSWGS = 0.600 from (-inf:inf) `ATTR(info="GATESIDE PARAMETER OF CAPACITANCE FOR JUNCTION DIODE, SOURCE SIDE (ASYMMETRICAL MODEL)");

[gjcoram]

In addition, the capacitance voltage parameters are temperature-adjusted without checking that their values remain positive.

// CAPACITANCE VOLTAGE PARAMETERS
pbs_t = PBS - (TPB * dT);
pbsws_t = PBSWS - (TPBSW * dT);
pbswgs_t = PBSWGS - (TPBSWG * dT);
pbd_t = PBD - (TPB * dT);
pbswd_t = PBSWD - (TPBSW * dT);
pbswgd_t = PBSWGD - (TPBSWG * dT);

If pbs_t is negative (and v_sbj > 0.0), we can get a negative argument to the logarithm:
cj_s = cjs_t * as * exp( - MJS * ln(1.0 + v_sbj / pbs_t ));

BSIM4 clamps PBS to 0.1:
if (model->BSIM4SbulkJctPotential < 0.1)
{ model->BSIM4SbulkJctPotential = 0.1;
fprintf(stderr, "Given pbs is less than 0.1. Pbs is set to 0.1.\n");