Add a simple quasi saturation model according to V. d'Alessandro e.a., 2001

src/spicelib/devices/vdmos/vdmos.c

@@ -79,6 +79,9 @@ IFparm VDMOSmPTable[] = { /* model parameters */
  IOP("rs",    VDMOS_MOD_RS,    IF_REAL,   "Source ohmic resistance"),
  IOP("rg",    VDMOS_MOD_RG,    IF_REAL,   "Gate ohmic resistance"),
 
+ /* quasi saturation */
+ IOP("rq",      VDMOS_MOD_RQ,      IF_REAL,   "Quasi saturation resistance fitting parameter"),
+ IOP("vq",      VDMOS_MOD_VQ,      IF_REAL,   "Quasi saturation voltage fitting parameter"),
  IOP("mtriode", VDMOS_MOD_MTRIODE, IF_REAL,   "Conductance multiplier in triode region"),
 
  /* weak inversion */

src/spicelib/devices/vdmos/vdmosdefs.h

@@ -319,7 +319,8 @@ typedef struct sVDMOSmodel {       /* model structure for a resistor */
     double VDMOSdrainResistance;
     double VDMOSsourceResistance;
     double VDMOSgateResistance;
-    double VDMOSsheetResistance;
+    double VDMOSqsResistance;
+    double VDMOSqsVoltage;
     double VDMOStransconductance;    /* input - use tTransconductance */
     double VDMOSoxideCapFactor;
     double VDMOSvt0; /* input - use tVto */
@@ -363,6 +364,9 @@ typedef struct sVDMOSmodel {       /* model structure for a resistor */
     unsigned VDMOSdrainResistanceGiven   :1;
     unsigned VDMOSsourceResistanceGiven  :1;
     unsigned VDMOSgateResistanceGiven    :1;
+    unsigned VDMOSqsResistanceGiven    :1;
+    unsigned VDMOSqsVoltageGiven    :1;
+    unsigned VDMOSqsGiven    :1;
     unsigned VDMOStransconductanceGiven  :1;
     unsigned VDMOSvt0Given   :1;
     unsigned VDIOgradCoeffGiven    :1;
@@ -426,6 +430,8 @@ enum {
     VDMOS_MOD_RD,
     VDMOS_MOD_RS,
     VDMOS_MOD_RG,
+    VDMOS_MOD_RQ,
+    VDMOS_MOD_VQ,
     VDMOS_MOD_IS,
     VDMOS_MOD_VJ,
     VDMOS_MOD_CJ,

src/spicelib/devices/vdmos/vdmosload.c

@@ -590,6 +590,24 @@ bypass :
                 (ceqbd - cdreq + model->VDMOStype * ceqgd);
             *(ckt->CKTrhs + here->VDMOSsNodePrime) +=
                 cdreq + ceqbs + model->VDMOStype * ceqgs;
+
+
+            /* quasi saturation
+             * according to Vincenzo d'Alessandro's Quasi-Saturation Model, simplified:
+             V. D'Alessandro, F. Frisina, N. Rinaldi: A New SPICE Model of VDMOS Transistors
+             Including Thermal and Quasi-saturation Effects, 9th European Conference on Power
+             Electronics and applications (EPE), Graz, Austria, August 2001, pp. P.1 − P.10.
+             */
+            if (model->VDMOSqsGiven && (here->VDMOSmode == 1)) {
+                double vdsn = model->VDMOStype * (
+                    *(ckt->CKTrhsOld + here->VDMOSdNode) -
+                    *(ckt->CKTrhsOld + here->VDMOSsNode));
+                double rd = model->VDMOSdrainResistance + model->VDMOSqsResistance * 
+                    (vdsn / (vdsn + fabs(model->VDMOSqsVoltage)));
+                here->VDMOSdrainConductance = 1 / rd;
+            }
+
+
             /*
              *  load y matrix
              */

src/spicelib/devices/vdmos/vdmosmask.c

@@ -45,6 +45,12 @@ VDMOSmAsk(CKTcircuit *ckt, GENmodel *inst, int which, IFvalue *value)
         case VDMOS_MOD_RG:
             value->rValue = model->VDMOSgateResistance;
             return(OK);
+        case VDMOS_MOD_RQ:
+            value->rValue = model->VDMOSqsResistance;
+            return(OK);
+        case VDMOS_MOD_VQ:
+            value->rValue = model->VDMOSqsVoltage;
+            return(OK);
         case VDMOS_MOD_MTRIODE:
             value->rValue = model->VDMOSmtr;
             return(OK);

src/spicelib/devices/vdmos/vdmosmpar.c

@@ -47,6 +47,18 @@ VDMOSmParam(int param, IFvalue *value, GENmodel *inModel)
             model->VDMOSgateResistance = value->rValue;
             model->VDMOSgateResistanceGiven = TRUE;
             break;
+        case VDMOS_MOD_RQ:
+            model->VDMOSqsResistance = value->rValue;
+            model->VDMOSqsResistanceGiven = TRUE;
+            if (model->VDMOSqsVoltageGiven)
+                model->VDMOSqsGiven = TRUE;
+            break;
+        case VDMOS_MOD_VQ:
+            model->VDMOSqsVoltage = value->rValue;
+            model->VDMOSqsVoltageGiven = TRUE;
+            if (model->VDMOSqsResistanceGiven)
+                model->VDMOSqsGiven = TRUE;
+            break;
         case VDMOS_MOD_RB:
             model->VDIOresistance = value->rValue;
             model->VDIOresistanceGiven = TRUE;