From 57a0a5dec0d80f34a680514d1edef11e187a34b9 Mon Sep 17 00:00:00 2001
From: rlar <rlar>
Date: Sun, 17 Dec 2017 20:57:36 +0100
Subject: [PATCH] devices/bjt/bjttemp.c, bug fix, capacity temperature
 dependency
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Fix a very old bug in the implementation of the
  gummel-poon model formulas for the junction capacities.
  (already in spice3f4)
For unknown reasons, the same formulas in the
  diode mos1 mos2 mos6 jfet models
have been implemented correctly right from the beginning,
the typo was bjt specific.

Many Thanks for the concise and precise Bug Report
  provided by Schabo Rumanus on the ngspice-users mailing list
> To: ngspice-users@lists.sourceforge.net
> Subject: [Ngspice-users] Temperatursimulation von Sperrschichtkapazitäten

Many Thanks to Dietmar Warning for his thorough verification
  of this commit.
---
 src/spicelib/devices/bjt/bjttemp.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/spicelib/devices/bjt/bjttemp.c b/src/spicelib/devices/bjt/bjttemp.c
index a49fe7318..89e62c2c8 100644
--- a/src/spicelib/devices/bjt/bjttemp.c
+++ b/src/spicelib/devices/bjt/bjttemp.c
@@ -24,6 +24,7 @@ BJTtemp(GENmodel *inModel, CKTcircuit *ckt)
     BJTinstance *here;
     double xfc;
     double vt;
+    double vtnom;
     double ratlog;
     double ratio1;
     double factlog;
@@ -40,6 +41,7 @@ BJTtemp(GENmodel *inModel, CKTcircuit *ckt)
     for( ; model != NULL; model = model->BJTnextModel ) {
 
         if(!model->BJTtnomGiven) model->BJTtnom = ckt->CKTnomTemp;
+        vtnom = CONSTKoverQ * model->BJTtnom;
         fact1 = model->BJTtnom/REFTEMP;
 
         if(!model->BJTleakBEcurrentGiven) {
@@ -101,6 +103,7 @@ BJTtemp(GENmodel *inModel, CKTcircuit *ckt)
         for (here = model->BJTinstances; here != NULL ;
                 here=here->BJTnextInstance) {
 
+            double arg1, pbfact1, egfet1;
             if(!here->BJTdtempGiven)
                 here->BJTdtemp = 0.0;
 
@@ -162,6 +165,11 @@ BJTtemp(GENmodel *inModel, CKTcircuit *ckt)
             arg = -egfet/(2*CONSTboltz*here->BJTtemp)+
                     1.1150877/(CONSTboltz*(REFTEMP+REFTEMP));
             pbfact = -2*vt*(1.5*log(fact2)+CHARGE*arg);
+            egfet1 = 1.16-(7.02e-4*model->BJTtnom*model->BJTtnom)/
+                    (model->BJTtnom+1108);
+            arg1 = -egfet1/(2*CONSTboltz*model->BJTtnom)+
+                    1.1150877/(CONSTboltz*(REFTEMP+REFTEMP));
+            pbfact1 = -2*vtnom*(1.5*log(fact1)+CHARGE*arg1);
 
             ratlog = log(here->BJTtemp/model->BJTtnom);
             ratio1 = here->BJTtemp/model->BJTtnom -1;
@@ -200,7 +208,7 @@ BJTtemp(GENmodel *inModel, CKTcircuit *ckt)
             }
 
             if (model->BJTtlevc == 0) {
-                pbo = (model->BJTpotentialBE-pbfact)/fact1;
+                pbo = (model->BJTpotentialBE-pbfact1)/fact1;
                 gmaold = (model->BJTpotentialBE-pbo)/pbo;
                 here->BJTtBEcap = model->BJTdepletionCapBE/
                     (1+here->BJTtjunctionExpBE*
@@ -215,7 +223,7 @@ BJTtemp(GENmodel *inModel, CKTcircuit *ckt)
                 here->BJTtBEpot = model->BJTpotentialBE - model->BJTtvje*dt;
             }
             if (model->BJTtlevc == 0) {
-                pbo = (model->BJTpotentialBC-pbfact)/fact1;
+                pbo = (model->BJTpotentialBC-pbfact1)/fact1;
                 gmaold = (model->BJTpotentialBC-pbo)/pbo;
                 here->BJTtBCcap = model->BJTdepletionCapBC/
                     (1+here->BJTtjunctionExpBC*
@@ -230,7 +238,7 @@ BJTtemp(GENmodel *inModel, CKTcircuit *ckt)
                 here->BJTtBCpot = model->BJTpotentialBC - model->BJTtvjc*dt;
             }
             if (model->BJTtlevc == 0) {
-                pbo = (model->BJTpotentialSubstrate-pbfact)/fact1;
+                pbo = (model->BJTpotentialSubstrate-pbfact1)/fact1;
                 gmaold = (model->BJTpotentialSubstrate-pbo)/pbo;
                 here->BJTtSubcap = model->BJTcapSub/
                         (1+here->BJTtjunctionExpSub*