# Measuring transconductance of any circuit

May I know if the following transconductance measurement test circuit is correct because I am getting quite small Gm values ?

I suspect that I need to use some derivative function because changing the mosfets width by a large factor does not change the gm result much at all.

However, my test circuit is simulated in AC, not DC, therefore I really confuse if I should use derivative function or not ?

Note: X1 is a CMOS inverter

• Be aware that Gm rises to its maximum value for an inverter that is DC-biased about half-way (with Vdd of 3.3V, Vin=Vout=1.6v). You should be able to check SPICE output to see at what DC value of Vout is used by AC analysis. Commented Dec 17, 2018 at 15:08
• AC analysis will give you an approximation to the derivative, no need to apply it after. It is unclear in the tb where the AC source is. And the RC loading may or may not be sufficient (better with DC sources).
– HKOB
Commented Dec 17, 2018 at 15:23
• @HKOB See Vin with AC 1 source. Why and How "AC analysis will give you an approximation to the derivative" ? Commented Dec 17, 2018 at 15:48

I suspect that I need to use some derivative function

The $$\g_m\$$ of a transistor is indeed defined as the derivative:

$$g_m = \frac{\partial i_{DS}}{\partial v_{DS}}$$

But Spice will always be able to calculate it for you. It is actually one of those perks of how Spice actually solves any analysis! Solving any type of analysis in Spice is centered around Newton-Raphson's method, which is the multidimensional version of Newton's method which requires the derivative of every quantity to every other quantity, including $$\g_m\$$.

For AC analysis, Newton Raphson's method is first used to determine the operating point. Then the computed derivatives are re-used for the small-signal analysis result. This is therefore a linearized version of the circuit, where linearized means using the derivatives. So the results of an AC analysis will already use the derivatives, including $$\g_m\$$.

What I am more concerned about is you model statements. Ie. the lines:

.model n1 NMOS
.model p1 PMOS

I assume that the simulator will choose transistor LEVEL=1 by default, and some simulators will choose $$\Kp = 0\$$ for that, which directly relates to a $$\g_m = 0\$$. Try specifying that parameter and see if it makes a difference.

• I am not using LEVEL=1 transistor See github.com/promach/frequency_trap/blob/development/… BSIM4 model which is LEVEL=14 Commented Dec 18, 2018 at 0:55
• The generated netlist file indicates that you are not including those models correctly. Commented Dec 18, 2018 at 8:14
• the netlist file link you posted above does not match the schematics drawing in this thread. I will update the netlist once I find a suitable test schematics to measure transconductance correctly. Please be patient Commented Dec 18, 2018 at 14:37

AC analysis is a small-signal analysis. It computes the small-signal response on the output(s) when applying a small perturbance on the input(s) around the DC operating point. I do not know exactly how the simulator does it. As your tb looks now the AC source will set the DC value of Vin, which is probably not desired(?) when you have the feedback to set an operating point. Rather put the AC source from the large C to the inverter input. Or, without changes, I suppose you could in the AC analysis sweep the DC value of Vin at a fixed frequency.

Also, I would recommend to replace the RC load with a voltage source. If you always want to simulate around the operating point you can for instance use a dependent V source controlled by a replica circuit to set the output voltage and measure the output current. That method should remove any dependency you might see from the load.

Here's an example of what I meant with the replica circuit setup :

simulate this circuit – Schematic created using CircuitLab

• if I do not use large R*C time constant (connected in feedback to input in order to eliminate high frequency), I would not be able to set up a self-biasing condition in DC. I do not understand what you mean by "without changes, I suppose you could in the AC analysis sweep the DC value of Vin at a fixed frequency" ? Commented Dec 19, 2018 at 8:29
• @Sven See electronics.stackexchange.com/a/383579/36150 for the reason of using feedback RC circuitry Commented Dec 19, 2018 at 8:31
• Typo edit: I would not be able to set up a self-biasing DC condition within AC analysis Commented Dec 19, 2018 at 8:40
• @kevin998x I added an example setup with a replica circuit. You may or may not want to keep the output at the input operating point. At different output voltages (parts of your swing) gm and gm/gds will vary with the different Ids and Vds of the transistors.
– HKOB
Commented Dec 19, 2018 at 17:15
• the replica circuit seems redundant. Why not just a independent DC voltage source having a value of Vdd/2 (academically it is the middle voltage, Vm for CMOS inverter) to secure saturation modes for both mosfets ? Commented Dec 20, 2018 at 3:24

Please see the following test circuit (for CMOS inverter) that shows gm_pmos + gm_nmos = overall Gm

[phung@archlinux frequency_trap]\$ ngspice test_CMOS_Inverter.net
******
** ngspice-29 : Circuit level simulation program
** The U. C. Berkeley CAD Group
** Copyright 1985-1994, Regents of the University of California.
** Creation Date: Sun Nov 11 02:18:13 UTC 2018
******

Circuit: * gnetlist -l ../.. -g spice-noqsi -o test_cmos_inverter.net test_cmos_inverter.sch

Doing analysis at TEMP = 25.000000 and TNOM = 27.000000

No. of Data Rows : 100
* gnetlist -l ../.. -g spice-noqsi -o test_cmos_inverter.net test_cmos_inverter.sch
AC Analysis  Sun Dec 23 18:14:37  2018
--------------------------------------------------------------------------------
Index   frequency       @m.x1.m1[gm]
--------------------------------------------------------------------------------
0   1.000000e+00   2.080796e-03,   0.000000e+00
1   1.010101e+08   2.080796e-03,   0.000000e+00
2   2.020202e+08   2.080796e-03,   0.000000e+00
3   3.030303e+08   2.080796e-03,   0.000000e+00
4   4.040404e+08   2.080796e-03,   0.000000e+00
5   5.050505e+08   2.080796e-03,   0.000000e+00
6   6.060606e+08   2.080796e-03,   0.000000e+00
7   7.070707e+08   2.080796e-03,   0.000000e+00
8   8.080808e+08   2.080796e-03,   0.000000e+00
9   9.090909e+08   2.080796e-03,   0.000000e+00
10   1.010101e+09   2.080796e-03,   0.000000e+00
11   1.111111e+09   2.080796e-03,   0.000000e+00
12   1.212121e+09   2.080796e-03,   0.000000e+00
13   1.313131e+09   2.080796e-03,   0.000000e+00
14   1.414141e+09   2.080796e-03,   0.000000e+00
15   1.515152e+09   2.080796e-03,   0.000000e+00
16   1.616162e+09   2.080796e-03,   0.000000e+00
17   1.717172e+09   2.080796e-03,   0.000000e+00
18   1.818182e+09   2.080796e-03,   0.000000e+00
19   1.919192e+09   2.080796e-03,   0.000000e+00
20   2.020202e+09   2.080796e-03,   0.000000e+00
21   2.121212e+09   2.080796e-03,   0.000000e+00
22   2.222222e+09   2.080796e-03,   0.000000e+00
23   2.323232e+09   2.080796e-03,   0.000000e+00
24   2.424242e+09   2.080796e-03,   0.000000e+00
25   2.525253e+09   2.080796e-03,   0.000000e+00
26   2.626263e+09   2.080796e-03,   0.000000e+00
27   2.727273e+09   2.080796e-03,   0.000000e+00
28   2.828283e+09   2.080796e-03,   0.000000e+00
29   2.929293e+09   2.080796e-03,   0.000000e+00
30   3.030303e+09   2.080796e-03,   0.000000e+00
31   3.131313e+09   2.080796e-03,   0.000000e+00
32   3.232323e+09   2.080796e-03,   0.000000e+00
33   3.333333e+09   2.080796e-03,   0.000000e+00
34   3.434343e+09   2.080796e-03,   0.000000e+00
35   3.535354e+09   2.080796e-03,   0.000000e+00
36   3.636364e+09   2.080796e-03,   0.000000e+00
37   3.737374e+09   2.080796e-03,   0.000000e+00
38   3.838384e+09   2.080796e-03,   0.000000e+00
39   3.939394e+09   2.080796e-03,   0.000000e+00
40   4.040404e+09   2.080796e-03,   0.000000e+00
41   4.141414e+09   2.080796e-03,   0.000000e+00
42   4.242424e+09   2.080796e-03,   0.000000e+00
43   4.343434e+09   2.080796e-03,   0.000000e+00
44   4.444444e+09   2.080796e-03,   0.000000e+00
45   4.545455e+09   2.080796e-03,   0.000000e+00
46   4.646465e+09   2.080796e-03,   0.000000e+00
47   4.747475e+09   2.080796e-03,   0.000000e+00
48   4.848485e+09   2.080796e-03,   0.000000e+00
49   4.949495e+09   2.080796e-03,   0.000000e+00
50   5.050505e+09   2.080796e-03,   0.000000e+00
51   5.151515e+09   2.080796e-03,   0.000000e+00
52   5.252525e+09   2.080796e-03,   0.000000e+00
53   5.353535e+09   2.080796e-03,   0.000000e+00
54   5.454545e+09   2.080796e-03,   0.000000e+00

Index   frequency       @m.x1.m1[gm]
--------------------------------------------------------------------------------
55   5.555556e+09   2.080796e-03,   0.000000e+00
56   5.656566e+09   2.080796e-03,   0.000000e+00
57   5.757576e+09   2.080796e-03,   0.000000e+00
58   5.858586e+09   2.080796e-03,   0.000000e+00
59   5.959596e+09   2.080796e-03,   0.000000e+00
60   6.060606e+09   2.080796e-03,   0.000000e+00
61   6.161616e+09   2.080796e-03,   0.000000e+00
62   6.262626e+09   2.080796e-03,   0.000000e+00
63   6.363636e+09   2.080796e-03,   0.000000e+00
64   6.464646e+09   2.080796e-03,   0.000000e+00
65   6.565657e+09   2.080796e-03,   0.000000e+00
66   6.666667e+09   2.080796e-03,   0.000000e+00
67   6.767677e+09   2.080796e-03,   0.000000e+00
68   6.868687e+09   2.080796e-03,   0.000000e+00
69   6.969697e+09   2.080796e-03,   0.000000e+00
70   7.070707e+09   2.080796e-03,   0.000000e+00
71   7.171717e+09   2.080796e-03,   0.000000e+00
72   7.272727e+09   2.080796e-03,   0.000000e+00
73   7.373737e+09   2.080796e-03,   0.000000e+00
74   7.474747e+09   2.080796e-03,   0.000000e+00
75   7.575758e+09   2.080796e-03,   0.000000e+00
76   7.676768e+09   2.080796e-03,   0.000000e+00
77   7.777778e+09   2.080796e-03,   0.000000e+00
78   7.878788e+09   2.080796e-03,   0.000000e+00
79   7.979798e+09   2.080796e-03,   0.000000e+00
80   8.080808e+09   2.080796e-03,   0.000000e+00
81   8.181818e+09   2.080796e-03,   0.000000e+00
82   8.282828e+09   2.080796e-03,   0.000000e+00
83   8.383838e+09   2.080796e-03,   0.000000e+00
84   8.484848e+09   2.080796e-03,   0.000000e+00
85   8.585859e+09   2.080796e-03,   0.000000e+00
86   8.686869e+09   2.080796e-03,   0.000000e+00
87   8.787879e+09   2.080796e-03,   0.000000e+00
88   8.888889e+09   2.080796e-03,   0.000000e+00
89   8.989899e+09   2.080796e-03,   0.000000e+00
90   9.090909e+09   2.080796e-03,   0.000000e+00
91   9.191919e+09   2.080796e-03,   0.000000e+00
92   9.292929e+09   2.080796e-03,   0.000000e+00
93   9.393939e+09   2.080796e-03,   0.000000e+00
94   9.494949e+09   2.080796e-03,   0.000000e+00
95   9.595960e+09   2.080796e-03,   0.000000e+00
96   9.696970e+09   2.080796e-03,   0.000000e+00
97   9.797980e+09   2.080796e-03,   0.000000e+00
98   9.898990e+09   2.080796e-03,   0.000000e+00
99   1.000000e+10   2.080796e-03,   0.000000e+00
* gnetlist -l ../.. -g spice-noqsi -o test_cmos_inverter.net test_cmos_inverter.sch
AC Analysis  Sun Dec 23 18:14:37  2018
--------------------------------------------------------------------------------
Index   frequency       @m.x1.m4[gm]
--------------------------------------------------------------------------------
0   1.000000e+00   1.145951e-03,   0.000000e+00
1   1.010101e+08   1.145951e-03,   0.000000e+00
2   2.020202e+08   1.145951e-03,   0.000000e+00
3   3.030303e+08   1.145951e-03,   0.000000e+00
4   4.040404e+08   1.145951e-03,   0.000000e+00
5   5.050505e+08   1.145951e-03,   0.000000e+00
6   6.060606e+08   1.145951e-03,   0.000000e+00
7   7.070707e+08   1.145951e-03,   0.000000e+00
8   8.080808e+08   1.145951e-03,   0.000000e+00
9   9.090909e+08   1.145951e-03,   0.000000e+00
10   1.010101e+09   1.145951e-03,   0.000000e+00
11   1.111111e+09   1.145951e-03,   0.000000e+00
12   1.212121e+09   1.145951e-03,   0.000000e+00
13   1.313131e+09   1.145951e-03,   0.000000e+00
14   1.414141e+09   1.145951e-03,   0.000000e+00
15   1.515152e+09   1.145951e-03,   0.000000e+00
16   1.616162e+09   1.145951e-03,   0.000000e+00
17   1.717172e+09   1.145951e-03,   0.000000e+00
18   1.818182e+09   1.145951e-03,   0.000000e+00
19   1.919192e+09   1.145951e-03,   0.000000e+00
20   2.020202e+09   1.145951e-03,   0.000000e+00
21   2.121212e+09   1.145951e-03,   0.000000e+00
22   2.222222e+09   1.145951e-03,   0.000000e+00
23   2.323232e+09   1.145951e-03,   0.000000e+00
24   2.424242e+09   1.145951e-03,   0.000000e+00
25   2.525253e+09   1.145951e-03,   0.000000e+00
26   2.626263e+09   1.145951e-03,   0.000000e+00
27   2.727273e+09   1.145951e-03,   0.000000e+00
28   2.828283e+09   1.145951e-03,   0.000000e+00
29   2.929293e+09   1.145951e-03,   0.000000e+00
30   3.030303e+09   1.145951e-03,   0.000000e+00
31   3.131313e+09   1.145951e-03,   0.000000e+00
32   3.232323e+09   1.145951e-03,   0.000000e+00
33   3.333333e+09   1.145951e-03,   0.000000e+00
34   3.434343e+09   1.145951e-03,   0.000000e+00
35   3.535354e+09   1.145951e-03,   0.000000e+00
36   3.636364e+09   1.145951e-03,   0.000000e+00
37   3.737374e+09   1.145951e-03,   0.000000e+00
38   3.838384e+09   1.145951e-03,   0.000000e+00
39   3.939394e+09   1.145951e-03,   0.000000e+00
40   4.040404e+09   1.145951e-03,   0.000000e+00
41   4.141414e+09   1.145951e-03,   0.000000e+00
42   4.242424e+09   1.145951e-03,   0.000000e+00
43   4.343434e+09   1.145951e-03,   0.000000e+00
44   4.444444e+09   1.145951e-03,   0.000000e+00
45   4.545455e+09   1.145951e-03,   0.000000e+00
46   4.646465e+09   1.145951e-03,   0.000000e+00
47   4.747475e+09   1.145951e-03,   0.000000e+00
48   4.848485e+09   1.145951e-03,   0.000000e+00
49   4.949495e+09   1.145951e-03,   0.000000e+00
50   5.050505e+09   1.145951e-03,   0.000000e+00
51   5.151515e+09   1.145951e-03,   0.000000e+00
52   5.252525e+09   1.145951e-03,   0.000000e+00
53   5.353535e+09   1.145951e-03,   0.000000e+00
54   5.454545e+09   1.145951e-03,   0.000000e+00

Index   frequency       @m.x1.m4[gm]
--------------------------------------------------------------------------------
55   5.555556e+09   1.145951e-03,   0.000000e+00
56   5.656566e+09   1.145951e-03,   0.000000e+00
57   5.757576e+09   1.145951e-03,   0.000000e+00
58   5.858586e+09   1.145951e-03,   0.000000e+00
59   5.959596e+09   1.145951e-03,   0.000000e+00
60   6.060606e+09   1.145951e-03,   0.000000e+00
61   6.161616e+09   1.145951e-03,   0.000000e+00
62   6.262626e+09   1.145951e-03,   0.000000e+00
63   6.363636e+09   1.145951e-03,   0.000000e+00
64   6.464646e+09   1.145951e-03,   0.000000e+00
65   6.565657e+09   1.145951e-03,   0.000000e+00
66   6.666667e+09   1.145951e-03,   0.000000e+00
67   6.767677e+09   1.145951e-03,   0.000000e+00
68   6.868687e+09   1.145951e-03,   0.000000e+00
69   6.969697e+09   1.145951e-03,   0.000000e+00
70   7.070707e+09   1.145951e-03,   0.000000e+00
71   7.171717e+09   1.145951e-03,   0.000000e+00
72   7.272727e+09   1.145951e-03,   0.000000e+00
73   7.373737e+09   1.145951e-03,   0.000000e+00
74   7.474747e+09   1.145951e-03,   0.000000e+00
75   7.575758e+09   1.145951e-03,   0.000000e+00
76   7.676768e+09   1.145951e-03,   0.000000e+00
77   7.777778e+09   1.145951e-03,   0.000000e+00
78   7.878788e+09   1.145951e-03,   0.000000e+00
79   7.979798e+09   1.145951e-03,   0.000000e+00
80   8.080808e+09   1.145951e-03,   0.000000e+00
81   8.181818e+09   1.145951e-03,   0.000000e+00
82   8.282828e+09   1.145951e-03,   0.000000e+00
83   8.383838e+09   1.145951e-03,   0.000000e+00
84   8.484848e+09   1.145951e-03,   0.000000e+00
85   8.585859e+09   1.145951e-03,   0.000000e+00
86   8.686869e+09   1.145951e-03,   0.000000e+00
87   8.787879e+09   1.145951e-03,   0.000000e+00
88   8.888889e+09   1.145951e-03,   0.000000e+00
89   8.989899e+09   1.145951e-03,   0.000000e+00
90   9.090909e+09   1.145951e-03,   0.000000e+00
91   9.191919e+09   1.145951e-03,   0.000000e+00
92   9.292929e+09   1.145951e-03,   0.000000e+00
93   9.393939e+09   1.145951e-03,   0.000000e+00
94   9.494949e+09   1.145951e-03,   0.000000e+00
95   9.595960e+09   1.145951e-03,   0.000000e+00
96   9.696970e+09   1.145951e-03,   0.000000e+00
97   9.797980e+09   1.145951e-03,   0.000000e+00
98   9.898990e+09   1.145951e-03,   0.000000e+00
99   1.000000e+10   1.145951e-03,   0.000000e+00
* gnetlist -l ../.. -g spice-noqsi -o test_cmos_inverter.net test_cmos_inverter.sch
AC Analysis  Sun Dec 23 18:14:37  2018
--------------------------------------------------------------------------------
Index   frequency       gm
--------------------------------------------------------------------------------
0   1.000000e+00   6.338799e-12,   3.979701e-09
1   1.010101e+08   3.226539e-03,   2.589921e-05
2   2.020202e+08   3.226695e-03,   1.295023e-05
3   3.030303e+08   3.226724e-03,   8.633565e-06
4   4.040404e+08   3.226734e-03,   6.475194e-06
5   5.050505e+08   3.226738e-03,   5.180163e-06
6   6.060606e+08   3.226741e-03,   4.316806e-06
7   7.070707e+08   3.226742e-03,   3.700121e-06
8   8.080808e+08   3.226743e-03,   3.237607e-06
9   9.090909e+08   3.226744e-03,   2.877873e-06
10   1.010101e+09   3.226745e-03,   2.590086e-06
11   1.111111e+09   3.226745e-03,   2.354624e-06
12   1.212121e+09   3.226745e-03,   2.158406e-06
13   1.313131e+09   3.226745e-03,   1.992375e-06
14   1.414141e+09   3.226746e-03,   1.850062e-06
15   1.515152e+09   3.226746e-03,   1.726725e-06
16   1.616162e+09   3.226746e-03,   1.618805e-06
17   1.717172e+09   3.226746e-03,   1.523581e-06
18   1.818182e+09   3.226746e-03,   1.438938e-06
19   1.919192e+09   3.226746e-03,   1.363204e-06
20   2.020202e+09   3.226746e-03,   1.295044e-06
21   2.121212e+09   3.226746e-03,   1.233375e-06
22   2.222222e+09   3.226746e-03,   1.177313e-06
23   2.323232e+09   3.226746e-03,   1.126125e-06
24   2.424242e+09   3.226746e-03,   1.079203e-06
25   2.525253e+09   3.226746e-03,   1.036035e-06
26   2.626263e+09   3.226746e-03,   9.961877e-07
27   2.727273e+09   3.226746e-03,   9.592918e-07
28   2.828283e+09   3.226746e-03,   9.250314e-07
29   2.929293e+09   3.226746e-03,   8.931338e-07
30   3.030303e+09   3.226746e-03,   8.633627e-07
31   3.131313e+09   3.226747e-03,   8.355122e-07
32   3.232323e+09   3.226747e-03,   8.094025e-07
33   3.333333e+09   3.226747e-03,   7.848751e-07
34   3.434343e+09   3.226747e-03,   7.617906e-07
35   3.535354e+09   3.226747e-03,   7.400251e-07
36   3.636364e+09   3.226747e-03,   7.194689e-07
37   3.737374e+09   3.226747e-03,   7.000238e-07
38   3.838384e+09   3.226747e-03,   6.816021e-07
39   3.939394e+09   3.226747e-03,   6.641251e-07
40   4.040404e+09   3.226747e-03,   6.475220e-07
41   4.141414e+09   3.226747e-03,   6.317288e-07
42   4.242424e+09   3.226747e-03,   6.166876e-07
43   4.343434e+09   3.226747e-03,   6.023461e-07
44   4.444444e+09   3.226747e-03,   5.886564e-07
45   4.545455e+09   3.226747e-03,   5.755751e-07
46   4.646465e+09   3.226747e-03,   5.630626e-07
47   4.747475e+09   3.226747e-03,   5.510826e-07
48   4.848485e+09   3.226747e-03,   5.396017e-07
49   4.949495e+09   3.226747e-03,   5.285894e-07
50   5.050505e+09   3.226747e-03,   5.180176e-07
51   5.151515e+09   3.226747e-03,   5.078604e-07
52   5.252525e+09   3.226747e-03,   4.980939e-07
53   5.353535e+09   3.226747e-03,   4.886959e-07
54   5.454545e+09   3.226747e-03,   4.796459e-07

Index   frequency       gm
--------------------------------------------------------------------------------
55   5.555556e+09   3.226747e-03,   4.709251e-07
56   5.656566e+09   3.226747e-03,   4.625157e-07
57   5.757576e+09   3.226747e-03,   4.544014e-07
58   5.858586e+09   3.226747e-03,   4.465669e-07
59   5.959596e+09   3.226747e-03,   4.389980e-07
60   6.060606e+09   3.226747e-03,   4.316813e-07
61   6.161616e+09   3.226747e-03,   4.246046e-07
62   6.262626e+09   3.226747e-03,   4.177561e-07
63   6.363636e+09   3.226747e-03,   4.111251e-07
64   6.464646e+09   3.226747e-03,   4.047013e-07
65   6.565657e+09   3.226747e-03,   3.984751e-07
66   6.666667e+09   3.226747e-03,   3.924376e-07
67   6.767677e+09   3.226747e-03,   3.865803e-07
68   6.868687e+09   3.226747e-03,   3.808953e-07
69   6.969697e+09   3.226747e-03,   3.753751e-07
70   7.070707e+09   3.226747e-03,   3.700126e-07
71   7.171717e+09   3.226747e-03,   3.648011e-07
72   7.272727e+09   3.226747e-03,   3.597345e-07
73   7.373737e+09   3.226747e-03,   3.548066e-07
74   7.474747e+09   3.226747e-03,   3.500119e-07
75   7.575758e+09   3.226747e-03,   3.453451e-07
76   7.676768e+09   3.226747e-03,   3.408011e-07
77   7.777778e+09   3.226747e-03,   3.363751e-07
78   7.878788e+09   3.226747e-03,   3.320626e-07
79   7.979798e+09   3.226747e-03,   3.278593e-07
80   8.080808e+09   3.226747e-03,   3.237610e-07
81   8.181818e+09   3.226747e-03,   3.197640e-07
82   8.282828e+09   3.226747e-03,   3.158644e-07
83   8.383838e+09   3.226747e-03,   3.120588e-07
84   8.484848e+09   3.226747e-03,   3.083438e-07
85   8.585859e+09   3.226747e-03,   3.047162e-07
86   8.686869e+09   3.226747e-03,   3.011730e-07
87   8.787879e+09   3.226747e-03,   2.977113e-07
88   8.888889e+09   3.226747e-03,   2.943282e-07
89   8.989899e+09   3.226747e-03,   2.910211e-07
90   9.090909e+09   3.226747e-03,   2.877876e-07
91   9.191919e+09   3.226747e-03,   2.846251e-07
92   9.292929e+09   3.226747e-03,   2.815313e-07
93   9.393939e+09   3.226747e-03,   2.785041e-07
94   9.494949e+09   3.226747e-03,   2.755413e-07
95   9.595960e+09   3.226747e-03,   2.726409e-07
96   9.696970e+09   3.226747e-03,   2.698008e-07
97   9.797980e+09   3.226747e-03,   2.670194e-07
98   9.898990e+09   3.226747e-03,   2.642947e-07
99   1.000000e+10   3.226747e-03,   2.616251e-07
ngspice 1219 ->