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ngspice
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To achieve convergence, 1 Ohm resistor on source side 

for current measurement, 1 Ohm resistor in series to
gate node with parallel current source.
This commit is contained in:
Holger Vogt 2026-05-25 16:12:18 +02:00
parent 5dd666d5b0
commit 6af77571e6
1 changed files with 26 additions and 15 deletions
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41
src/frontend/inpdeg.c
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@ -2,7 +2,7 @@
Read and parse the .agemodel parameters of the ngspice netlist
Store them in a hash table ageparams
Copyright Holger Vogt 2025
Copyright Holger Vogt 2026
License: Modified BSD
*/
@ -443,7 +443,7 @@ static int add_degmodel(struct card* deck, double* result) {
char* dtok, * gtok, * stok, * intok;
static int numvm = 0, numvg = 0;
char* nline[3]; /* three new lines to be added to netlist */
char* nline[4]; /* three new lines to be added to netlist */
char* curr_line = deck->line;
intok = gettok_instance(&curr_line); /* skip instance name */
dtok = gettok_node(&curr_line); /* get drain, gate, and source tokens */
@ -469,20 +469,31 @@ static int add_degmodel(struct card* deck, double* result) {
vts = TRUE;
}
/* gate voltage shift */
if (vts)
// nline[0] = tprintf("Vg%d intern_%s %s %e\n", numvg++, gtok, gtok, result[0]);
nline[0] = tprintf("Vg%s intern_%s %s %e\n", intok, gtok, gtok, result[0]);
else
nline[0] = NULL;
/* drain current reduction */
if (currd) {
/* current measurement at source side */
nline[1] = tprintf("Vm%s intern_%s %s 0\n", intok, stok, stok);
/* parallel drain current with CCCS */
nline[2] = tprintf("F%s %s %s Vm%s %e\n", intok, dtok, stok, intok, currdeg);
if (vts) {
/* no series voltage source, but resistor 1 Ohm with parallel current source
to achieve convergence */
nline[0] = tprintf("ig%s intern_%s intern_%s %e\n", intok, gtok, gtok, result[0]);
nline[1] = tprintf("rp%s intern_%s %s 1\n", intok, gtok, gtok);
}
else
nline[1] = nline[2] = NULL;
nline[0] = nline[1] = NULL;
/* drain current reduction */
if (currd) {
#if (0)
/* current measurement at source side */
nline[2] = tprintf("vm%s intern_%s %s 0\n", intok, stok, stok);
/* parallel drain current with CCCS */
nline[3] = tprintf("f%s %s %s vm%s %e\n", intok, dtok, stok, intok, currdeg);
#else
/* current measurement at source side with 1 Ohm series resistor */
nline[2] = tprintf("rm%s intern_%s %s 1\n", intok, stok, stok);
/* parallel drain current with B source */
nline[3] = tprintf("b%s %s %s i=v(intern_%s, %s) * %e\n", intok, dtok, stok, stok, stok, currdeg);
#endif
}
else
nline[2] = nline[3] = NULL;
/* modify the instance line */
char* instline;
@ -499,7 +510,7 @@ static int add_degmodel(struct card* deck, double* result) {
}
/* attach to the netlist */
int ii;
for (ii = 0; ii < 3; ii++) {
for (ii = 0; ii < 4; ii++) {
if (nline[ii])
insert_new_line(deck, nline[ii], deck->linenum + 1, deck->linenum_orig, deck->linesource);
}