Added old code to jfetload.c ad updated documentation.

ChangeLog

@@ -1,8 +1,12 @@
 2003-12-26  Paolo Nenzi <p.nenzi@ieee.org>
 
-	* src/spicelibe/devices/jfet/*: Added parallel multiplier and
+	* src/spicelib/devices/jfet/*: Added parallel multiplier and
 	  "dtemp" parameter.
 	  
+	* src/spicelib/devices/jfet/jfetload.c: reintroduces the old model
+	  code, superseded by Sydney code (Parker Skellern). The code is
+	  not useed but is left as reference.   
+	
 	* DEVICES: Updated jfet status
 	
 	* tests/jfet, tests/jfet/jfet_vds-vgs.cir: added jfet directory 

DEVICES

@@ -181,6 +181,7 @@ JFET  - Junction Field Effect transistor
 	
 	Enhancements over the original model:
 	
+	- Alan Gillespie's modified diode model
 	- Parallel multiplier
 	- Instance temperature as difference for circuit temperature
         

src/spicelib/devices/jfet/jfetload.c

@@ -322,6 +322,78 @@ JFETload(GENmodel *inModel, CKTcircuit *ckt)
                     }
                 }
             }
+
+#ifdef notdef
+	    /* The original section is now commented out */
+	    /* end Sydney University mod */
+            /*
+             *   compute drain current and derivitives for normal mode 
+             */
+            if (vds >= 0) {
+                vgst=vgs-model->JFETthreshold;
+                /*
+                 *   normal mode, cutoff region 
+                 */
+                if (vgst <= 0) {
+                    cdrain=0;
+                    gm=0;
+                    gds=0;
+                } else {
+                    betap=beta*(1+model->JFETlModulation*vds);
+                    twob=betap+betap;
+                    if (vgst <= vds) {
+                        /*
+                         *   normal mode, saturation region 
+                         */
+                        cdrain=betap*vgst*vgst;
+                        gm=twob*vgst;
+                        gds=model->JFETlModulation*beta*vgst*vgst;
+                    } else {
+                        /*
+                         *   normal mode, linear region 
+                         */
+                        cdrain=betap*vds*(vgst+vgst-vds);
+                        gm=twob*vds;
+                        gds=twob*(vgst-vds)+model->JFETlModulation*beta*
+                                vds*(vgst+vgst-vds);
+                    }
+                }
+            } else {
+                /*
+                 *   compute drain current and derivitives for inverse mode 
+                 */
+                vgdt=vgd-model->JFETthreshold;
+                if (vgdt <= 0) {
+                    /*
+                     *   inverse mode, cutoff region 
+                     */
+                    cdrain=0;
+                    gm=0;
+                    gds=0;
+                } else {
+                    /*
+                     *   inverse mode, saturation region 
+                     */
+                    betap=beta*(1-model->JFETlModulation*vds);
+                    twob=betap+betap;
+                    if (vgdt <= -vds) {
+                        cdrain = -betap*vgdt*vgdt;
+                        gm = -twob*vgdt;
+                        gds = model->JFETlModulation*beta*vgdt*vgdt-gm;
+                    } else {
+                        /*
+                         *  inverse mode, linear region 
+                         */
+                        cdrain=betap*vds*(vgdt+vgdt+vds);
+                        gm=twob*vds;
+                        gds=twob*vgdt-model->JFETlModulation*beta*vds*
+                                (vgdt+vgdt+vds);
+                    }
+                }
+            }
+	    /* end of original section, now deleted (replaced w/SU mod */
+#endif
+
             /*
              *   compute equivalent drain current source 
              */