Results of the cold testing for identical JFETs
|
Set A |
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|---|---|---|---|---|---|---|---|---|---|
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# |
1 |
2 |
3 |
4 |
1 |
2 |
3 |
4 |
4 |
|
Condition |
|||||||||
|
mA/div |
1 |
1 |
1 |
1 |
0.2 |
0.2 |
0.2 |
0.2 |
0.2 |
|
Line 1 |
1.9 |
1.8 |
1.9 |
1.8 |
0.16 |
0.13 |
0.06 |
0.1 |
0.38 |
|
Line 2 |
2.5 |
2.4 |
2.6 |
2.5 |
0.75 |
0.33 |
0.25 |
0.33 |
0.5 |
|
Line 3 |
3.1 |
3 |
3.1 |
3.2 |
1.2 |
0.66 |
0.58 |
0.69 |
0.65 |
|
Line 4 |
3.8 |
3.7 |
3.8 |
3.8 |
1.81 |
1.18 |
1.05 |
1.18 |
0.8 |
|
Line 5 |
4.6 |
4.5 |
4.6 |
4.7 |
- |
1.8 |
1.63 |
1.79 |
0.97 |
|
Set B |
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|---|---|---|---|---|---|---|---|---|---|
|
# |
1 |
2 |
3 |
4 |
1 |
2 |
3 |
4 |
4 |
|
Condition |
|||||||||
|
mA/div |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
|
Line 1 |
5.2 |
5.2 |
5.4 |
5.4 |
3.1 |
3 |
3.2 |
3.1 |
4 |
|
Line 2 |
6.05 |
6.1 |
6.2 |
6.3 |
4.05 |
3.9 |
4.1 |
4 |
5.1 |
|
Line 3 |
6.9 |
7.05 |
7.1 |
7.3 |
5.15 |
5 |
5.1 |
5.05 |
6.2 |
|
Line 4 |
7.85 |
8 |
8 |
8.3 |
6.3 |
6.1 |
6.3 |
6.2 |
7.5 |
|
Line 5 |
8.8 |
9 |
9 |
9.4 |
7.55 |
7.3 |
7.5 |
7.5 |
8.6? |
FET #4 of Set B for the final cold torture trial had a nearly invisable fifth line. I could see the point at the end of the line, so I extrapolated backwards and made an assumption that this value of 8.6mA was appropriate.
These are all p-channel JFETs (J270/SST270). w=warm, c=cold, c-t= cold “tortured”. All values for the lines are in mA. All JFETs were matched previously warm, so these sets were pre-determined.
Comparing warm and cold, Set B, which was considered less well matched than Set A under warm testing, appears to be the better of the two sets hot and cold, looking at the range at which these values change. Set A is stil very good, however. There seems to be some discrepency in the values, as Set B appears to always be in the 1 mA range whilie Set A cold is in the 0.1 mA range. I will analyse this further. It also appears that the mA values could be negative as opposed to postitive going by Output Characteristics diagram 3 on page 8-3 of the Vishay J270/J271 data sheet. This is a minor thing, as I can simply denote the values as negative instead.
