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Old 4th December 2005, 04:50 PM   #1
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Default cheap amp can tip142 and 147 be replaced by bjts

Many thanks to everyone who replied to my previous post(building amps)
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Old 4th December 2005, 05:08 PM   #2
CBS240 is offline CBS240  United States
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Tip142/147 are darlington BJT's. So, yes they can be replaced by BJT's, but they must be darlington since that is what the circuit is biased for. The Vbe is 1.2V instead of 0.6V because the driver is integrated in with the outputs. The temperature coeffecient of the first transistor is multiplied by that of the second as is beta. This is what gives them a poor temperature coeffecient but high current gain and will require them to be thermally compensated or thermal runaway will occur. Vbe multiplier will work, but you might use a darlington transistor for this one too.

PS
Watch out for fakes as I have seen many fake TIP14*'s. Many fakes have undersized dies so they slack on SOA.
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Old 4th December 2005, 05:38 PM   #3
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Default hi thanx for reply i did get some fake trannys

Hi all ordered some bd250 and 249s,i had my suspicions when i had to bend the legs over on the bd249s,and one of the legs snapped ,they were so thin and smaller in thickness,leg length than the bd250.,which were the usual thick case long legged (thick)....

Bloody idiots,you try and build something and the parts you buy wreck it in less than a second...

Got my parts from East london components...
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Old 4th December 2005, 06:51 PM   #4
CBS240 is offline CBS240  United States
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TI use to run a semi factory in Morocco, but I think someone else owns it now. It still makes TIP devices and has MOROCCO printed on them. They are usually legit. Mospec also manufactures those parts legitamately from Taiwan, I think. I ordered some TIP141/146's from Mouser, and the 146's were from Mospec, but the 141's were fakes. The fakes blew out way before they were suppose to. None of the 146's failed under same conditions. People will take dies of inferior components, put them in the right pakage and sell them as genuine components because they can make money at it. It sucks, but if you shop by price, you may very well end up with fake components.

Check out this thread for more info...

counterfiet sa1943's ??


So don't feel to bad, your not alone with this issue.
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Old 5th December 2005, 12:28 AM   #5
anatech is offline anatech  Canada
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So true ....

-Chris
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