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Hi, I have what I hope is a really simple question, which I have been unable to find by rtfm. I have a single fet audio amplifier, I'll put the net file below, and no matter what I do, and I've been poking at this for hours, ngspice can't seem to locate an operating point. First off, the operating point for the fet is set by two 1m bias resistors. Those resistors would have to change value to find a different operating point, am I correct? How would ngspice know to do this?? Seems like there is some missing puzzle piece the manual fails to mention. Second, I don't care if it finds the exact center operating point, I happen to know if I hook this circuit up on a perfboard it will work just fine, and besides, every transistor is different so I'm just looking for an approximate answer. So here is the complaint I get from ngspice:
------------------------------
Doing analysis at TEMP = 300.150000 and TNOM = 300.150000
Warning: v1: has no value, DC 0 assumed
Warning: singular matrix: check nodes 2n5245 and 2n5245
Note: starting dynamic Gmin stepping
Trying gmin = 1.0000E-03 Note: One successful Gmin step
Trying gmin = 1.0000E-04 Note: One successful Gmin step
Trying gmin = 1.0000E-05 Note: One successful Gmin step
Trying gmin = 1.0000E-06 Note: One successful Gmin step
Trying gmin = 1.0000E-07 Note: One successful Gmin step
Trying gmin = 1.0000E-08 Note: One successful Gmin step
Trying gmin = 1.0000E-09 Note: One successful Gmin step
Trying gmin = 1.0000E-10 Note: One successful Gmin step
Trying gmin = 1.0000E-11 Note: One successful Gmin step
Trying gmin = 1.0000E-12 Note: One successful Gmin step
Trying gmin = 1.0000E-12 Note: One successful Gmin step
Warning: singular matrix: check nodes 2n5245 and 2n5245
Warning: Dynamic Gmin stepping failed
Note: starting source stepping
Supplies reduced to 0.0000% Warning: singular matrix: check nodes 2n5245 and 2n5245
Trying gmin = 1.0000E-02 Note: One successful Gmin step
Trying gmin = 1.0000E-03 Note: One successful Gmin step
Trying gmin = 1.0000E-04 Note: One successful Gmin step
Trying gmin = 1.0000E-05 Note: One successful Gmin step
Trying gmin = 1.0000E-06 Note: One successful Gmin step
Trying gmin = 1.0000E-07 Note: One successful Gmin step
Trying gmin = 1.0000E-08 Note: One successful Gmin step
Trying gmin = 1.0000E-09 Note: One successful Gmin step
Trying gmin = 1.0000E-10 Note: One successful Gmin step
Trying gmin = 1.0000E-11 Note: One successful Gmin step
Trying gmin = 1.0000E-12 Note: One successful Gmin step
Note: One successful source step
Supplies reduced to 0.1000% Warning: singular matrix: check nodes 2n5245 and 2n5245
Supplies reduced to 0.0000% Warning: singular matrix: check nodes 2n5245 and 2n5245
Warning: source stepping failed
DC solution failed -
Last Node Voltages
------------------
Node Last Voltage Previous Iter
---- ------------ -------------
1 -2.76707e-149 5.67409e-156
+9v -1.50823e-147 0
n0 0 0
4 0 0
3 1.30053e-143 1.0803e-157
2 -1.48056e-141 -5.78212e-156
2n5245 0 0
v1#branch 0 0
doAnalyses: iteration limit reached
op simulation(s) aborted
---------------------------------
And here is the .net file:
* Spice netlister for gnetlist
R5 1 +9V 1M
V1 n0 0 AC
R4 0 4 100K
R3 0 3 470
Q1 1 3 2 2N5245
R2 2 +9V 1K
R1 0 1 1M
C3 2 4 4.7uf
C2 3 0 .052uf
C1 n0 1 4.7uf
.END
My guess is there is something very simple and stupid I am doing wrong. This is such a basic circuit, this can't be that hard. Has anyone else run into this?
-Sean
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