Need help choosing a PNP transistor

When I power the base, I am cutting off the current flow through the Collector and Emitter.

However, when the base is off, I will need to conduct 4.2W through the transistor.Now, I am having trouble sourcing a transistor for this situation.

This is for a automotive part, in the end. So, if anyone has ever worked in that industry, what % do you go over the bare minimum ratings per transistor? No one here at this job seems to want to help me. The curse of being a contractor.

Cabe

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BinaryConstruct over 15 years ago

You might try something like this 5W P-Channel D-MOS transistor:

http://www.nxp.com/documents/data_sheet/BSP250.pdf

I don't work in the industry or know what percent over min tolerance you should use, but I have something very similar before in automotive audio and lighting applications.

edit:
here is a mouser link
http://www.mouser.com/ProductDetail/NXP-Semiconductors/BSP250115/?qs=sGAEpiMZZMv4eh0jmGe026yHc6TYsfYwAgT5%252bsU1GFk%3d
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Catwell over 15 years ago in reply to BinaryConstruct

BinaryConstruct,

On a second look, I will go with your P-channel mosfet. Thanks alot.

I will post a schematic soon.

Cabe
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enrico.migchels over 15 years ago in reply to Catwell

Hi Cabe,

Probably you are better off driving a N-channel mosfet in the negative rail of the power supply. This has several advantages: N-Channel has lower RDS(on) and the drive circuit is more simple. The FET can even be driven from a normal uc-output.

Best regards, Enrico Migchels
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Catwell over 15 years ago in reply to enrico.migchels

Enrico,

You are always one step ahead of me in your suggestions. I just found that an N-channel Mosfet would be best for my design, and then I read your reply. If, I only read it first.

I want to use it to cut the power to a LED. My plan is to activate it with a inverting transistor.

Let's see if Multisim agrees with us too.

Cabe
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Catwell over 15 years ago in reply to enrico.migchels

Enrico,

You are always one step ahead of me in your suggestions. I just found that an N-channel Mosfet would be best for my design, and then I read your reply. If, I only read it first.

I want to use it to cut the power to a LED. My plan is to activate it with a inverting transistor.

Let's see if Multisim agrees with us too.

Cabe
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