mos1...3: set channel thermal noise to 0 in subthreshold range for nlev=3

src/spicelib/devices/mos1/mos1noi.c

@@ -128,12 +128,13 @@ MOS1noise(int mode, int operation, GENmodel * genmodel, CKTcircuit * ckt,
                                 /* linear region */
                                 alpha = 1.0 - (vds*inst->MOS1mode/(model->MOS1type*inst->MOS1vdsat));
                             }
+                            beta = inst->MOS1tTransconductance * inst->MOS1m *
+                                   inst->MOS1w/(inst->MOS1l - 2 * model->MOS1latDiff);
+                            Sid = 2.0 / 3.0 * beta * vgst * (1.0+alpha+alpha*alpha) / (1.0+alpha) * model->MOS1gdsnoi;
                         } else {
-                            alpha = 0.0;
+                            /* subthreshold region */
+                            Sid = 0.0;
                         }
-                        beta = inst->MOS1tTransconductance * inst->MOS1m *
-                                   inst->MOS1w/(inst->MOS1l - 2 * model->MOS1latDiff);
-                        Sid = 2.0 / 3.0 * beta * vgst * (1.0+alpha+alpha*alpha) / (1.0+alpha) * model->MOS1gdsnoi;
                     }
 
                     NevalSrcInstanceTemp( & noizDens[MOS1IDNOIZ], & lnNdens[MOS1IDNOIZ],

src/spicelib/devices/mos2/mos2noi.c

@@ -117,12 +117,13 @@ MOS2noise(int mode, int operation, GENmodel * genmodel, CKTcircuit * ckt,
                                 /* linear region */
                                 alpha = 1.0 - (vds*inst->MOS2mode/(model->MOS2type*inst->MOS2vdsat));
                             }
+                            beta = inst->MOS2tTransconductance * inst->MOS2m *
+                                   inst->MOS2w/(inst->MOS2l - 2 * model->MOS2latDiff);
+                            Sid = 2.0 / 3.0 * beta * vgst * (1.0+alpha+alpha*alpha) / (1.0+alpha) * model->MOS2gdsnoi;
                         } else {
-                            alpha = 0.0;
+                            /* subthreshold region */
+                            Sid = 0.0;
                         }
-                        beta = inst->MOS2tTransconductance * inst->MOS2m *
-                                   inst->MOS2w/(inst->MOS2l - 2 * model->MOS2latDiff);
-                        Sid = 2.0 / 3.0 * beta * vgst * (1.0+alpha+alpha*alpha) / (1.0+alpha) * model->MOS2gdsnoi;
                     }
 
                     NevalSrcInstanceTemp( & noizDens[MOS2IDNOIZ], & lnNdens[MOS2IDNOIZ],

src/spicelib/devices/mos3/mos3noi.c

@@ -117,12 +117,13 @@ MOS3noise(int mode, int operation, GENmodel * genmodel, CKTcircuit * ckt,
                                 /* linear region */
                                 alpha = 1.0 - (vds*inst->MOS3mode/(model->MOS3type*inst->MOS3vdsat));
                             }
+                            beta = inst->MOS3tTransconductance * inst->MOS3m *
+                                   inst->MOS3w/(inst->MOS3l - 2 * model->MOS3latDiff);
+                            Sid = 2.0 / 3.0 * beta * vgst * (1.0+alpha+alpha*alpha) / (1.0+alpha) * model->MOS3gdsnoi;
                         } else {
-                            alpha = 0.0;
+                            /* subthreshold region */
+                            Sid = 0.0;
                         }
-                        beta = inst->MOS3tTransconductance * inst->MOS3m *
-                                   inst->MOS3w/(inst->MOS3l - 2 * model->MOS3latDiff);
-                        Sid = 2.0 / 3.0 * beta * vgst * (1.0+alpha+alpha*alpha) / (1.0+alpha) * model->MOS3gdsnoi;
                     }
 
                     NevalSrcInstanceTemp( & noizDens[MOS3IDNOIZ], & lnNdens[MOS3IDNOIZ],