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Old 16th July 2010, 05:36 PM   #1801
Salas is offline Salas  Greece
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Any stable DC source, its only a utility. Get a 2SK170 low IDSS, 2N5459 ,or any other 5-6mA IDSS NJFET, connect its drain at B(+), connect its G&S together, crock lead LED's anode there too. Return cathode to (-). Measure Vf across lit LED. Stick it on paper, note its Vf. Repeat for some. Do the sorting later picking from the noted bunch. Alternative and more precise to a resistor.
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Old 16th July 2010, 05:53 PM   #1802
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Thanks Salas,
I was just wondering about the method, stable DC source.
I've done the matching 3 times, very close measures.
I'll try to match 2SK170 too
Schematic here : Transistor matching
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Old 16th July 2010, 05:59 PM   #1803
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Just that is enough. Let the fets stabilize for 3 mins, and watch not to short the dvm, it will blow a fuse.
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Old 16th July 2010, 08:12 PM   #1804
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Thank you for the advices !
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Old 18th July 2010, 07:24 PM   #1805
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2SK170BL Matching session today about 100 units.
Results using the previous posted link schema :
6.51/6.52 - 6.61/6.62 - 6.67/6.67 - 6.95/6.96
7.11/7.12/7.13 - 7.17/7.18 - 7.26/7.27 - 7.39/7.39 - 7.48/7.49 - 7.65/7.65 - 7.94/7.94
8.16/8.16/8.16 - 8.49/8.49 - 8.81/8.81 - 8.83/8.83 - 8.96/8.97
9.93/9.94
10.91/10.92

About 18 pairs/trio found.

Question
Which of them should I prefer using in Q1/2 and Q3/4 position as shown in this pic ?
Thanks
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Old 18th July 2010, 07:33 PM   #1806
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7.12/7.11 - 7.17/7.18 1,2,3,4
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Old 18th July 2010, 07:42 PM   #1807
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Thank you Salas
It will equilibrate the values in this order Q1:7.12/Q3:7.17 and Q2:7.11/Q4:7.18
Am I right ?
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Old 18th July 2010, 07:43 PM   #1808
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No, fit just as I gave the order.
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Old 18th July 2010, 07:44 PM   #1809
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Yes Sir !
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Old 18th July 2010, 07:47 PM   #1810
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At ease!
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