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I am using a P-Channel MOSFET to build a buck converter and change 12VDC, 2A (from a 12V battery) to 5VDC, 2A (for cell phone charging), should I use a MOSFET rated for 20V, 2A or -20V, -2A?

I am new to this, so sorry for the basic question. A simple one word answer will do, don't trouble yourselves too much with an explanation.

Thanks!!!!

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20V (or -20V) and 2A (or -2A) is probably OK. I'd concern myself with on-resistance too.

By the way, you won't be converting 12V at 2A to 5V at 2A - if your 5V load is 2A then the output power will be 10 watts and, given that a buck converter is 90% efficient, the input power will be 11 watts implying an input current of only 0.92 amps.

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  • \$\begingroup\$ You are correct about the 0.92 amps. My first statement was a typo. So would it be correct to say that I could use these two parts interchangeably? Would it not matter if I buy a MOSFET for -20v or 20v? \$\endgroup\$
    – sbrao
    May 6, 2015 at 14:20
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    \$\begingroup\$ A P channel mosfet might be specified as 20V or -20V - they mean the same thing in the context of this question. \$\endgroup\$
    – Andy aka
    May 6, 2015 at 14:38

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