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Author Topic: Circuit Design for Large LED matrix  (Read 10410 times)
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So logic level MOSFETs are really just useful for N-channel parts going to ground then.
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Yes, and for p-channel parts switching +5v. To switch higher voltages with a p-channel part, you need to level-shift the gate drive, and you can just as easily amplify it at the same time.
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So, since i'm switching such a large voltage source (relative to logic levels), could I have just as easily used PNP and NPN transistors on the anodes/cathodes instead of the npn+pFET combo on the anodes and npn on the cathodes?
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Take a look at this Maxim application note for the 8x8 matrix drive chip, the MAX7219/7221.
You are setting up to do the same.
http://www.maxim-ic.com/app-notes/index.mvp/id/1196
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So, since i'm switching such a large voltage source (relative to logic levels), could I have just as easily used PNP and NPN transistors on the anodes/cathodes instead of the npn+pFET combo on the anodes and npn on the cathodes?

You could have used a PNP transistor or power darlington, plus one additional resistor, in place of the P-channel mosfet. You would still need an NPN transistor to level shift the drive to the PNP transistor.
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