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2SD2385 + 2SB1556 Transistors

Will wonders never cease ? This place actually has a datasheet ! (they fail ed me so much I no longer bother, but at the end it said "PDF" so I got it)

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If you really cannot get them you can make Darlingtons, but I don't recomme nd it. However when you look at the internal diagram you see the the EB jun ction on a meter is not going to read like a Darlington because of the 100 ihm resistor across the EB junction of the output. You would only see the d rop of the driver EB junction. Depending on your meter it might read 0.100 higher, but will not read 1.2 volts as you might expect.

You are not ordering a million of these things, if the right part is a bit more expensive it is worth it. Like someone said B & D, but then I don't kn ow where you are. If not in the US, dealing internationally can be a PITA.

J
Reply to
jurb6006
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"fruittool"

** But you are an utter idiot.

.... Phil

Reply to
Phil Allison

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** Shame the schem in the above omits the reverse diode across the C and E terminals.

Easiest way to pick a power darlington with an ohm meter.

.... Phil

Reply to
Phil Allison

Actually it might not have one, there is no law.

With two resistors, a DVM and a 12 volt supply you can measure the hfe quite easily.

That 100 ohm resistor is much more important, otherwise the Icex of the first transistor at the very least will always be applied to the base of the second transistor. The Ice leakage numbers for the whole device would look like germanium.

J
Reply to
jurb6006

** Every darlington power transistor made has a reverse diode from C to E - it is part if the structure of the chip.

All power mosfets have a similar diode.

** But you gotta be real quick or the device will cook.

** Hogwash.

The 100ohm resistor is there to improve the switch off speed of the power transistor plus increase the breakdown voltage a little.

Leakage current in the driver transistor is only a few microamps, at most, a current level the output device can barely amplify at all.

.... Phil

Reply to
Phil Allison

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Reply to
Sofa Slug

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