Matching IRFP244 MOS-FETs - Page 4 - diyAudio
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Old 5th June 2011, 06:44 AM   #31
Join Date: Dec 2007
Went trough most of this before hope it may helps.

Frags posted a couple of SCH for differential testing in 9 December
Tanks again to Frags for ideas and help.
The 2 first pictures are his original work.

I have made up a little test rig with a CPU fan and a simple controller.
Just parts I had already and quite suprised on how well it works
may be handy as fan speed contreller later on.

It can dissipate well over 50W (done my matching at 26V and 2A) and keep temperature whiten + - 1 C of the 50 C I picked out of the hat.

While I measure one duda the next few are sitting on the plate getting worm.

I get Vgs to settle in a minute or so and at 50 C the effect of ambient temperature and air currents is greatly reduced.

Maybe at 30 C one may risk corrupting results Just by touching the little Bug...

QSP is doing same much more advanced testing and he posted a SCH for Tran conductance matching.

Although next on my list of to do things I have not tried that one out
But well worth a look at (just search for QSP posts as at the moment I have lost it)

Holco MFR 15ppm 2W for sale
Attached Images
File Type: jpg FRAG912diff_test.JPG (35.8 KB, 132 views)
File Type: jpg Frags912 2test2.jpg (37.3 KB, 134 views)
File Type: jpg MATCHING TEST RIG 001.jpg (593.5 KB, 116 views)
File Type: jpg MATCHING TEST RIG 002.jpg (620.3 KB, 110 views)
File Type: jpg MATCHING TEST RIG 003.jpg (622.8 KB, 105 views)
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Old 5th June 2011, 07:19 AM   #32
Join Date: Nov 2006
Location: Torpoint
Vgs is better generated with a stabilized voltage. I used an LM317.

Using the LM317 I was able to match sextets out of a batch of 50 to within 2% of each other.
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Old 6th June 2011, 11:22 AM   #33
Join Date: Nov 2006
Location: Torpoint
After the matching process I now have 26 x IRFP244s left over.

These have all gone through the matching process and will be supplied with the relevant data to enable you to pick out matched pairs and triplets.

50.00 the lot plus P&P.

Last edited by Andy5112405; 6th June 2011 at 11:30 AM.
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