logic mosfets versus regular mosfets

May 09, 2012 1 Replies

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panfilero 14 years ago

Hello, so I'm needing to interface some fets to some GPIO pins that have 5V logic levels, I have a bunch of these FDC3612 fets available to me which have a Vgs,th = 2V, then I see these logic level style fets like the FDV301N which have a Vgs,th = 1V... the logic level fet has a much higher Rds,on (5 ohms compared to .2 ohms or so), is the only thing that makes one of these better than the other to use with logic the Vgs,th values? If I had a 3.3V system, I could see the lower one being better.... but at 5V does it really have an advantage?

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John Larkin 14 years ago

Vth doesn't matter much. What's important is the drain I:V curve at 5 volts on the gate, Fig 1. The 3612 looks rasily good for its rated 2.6 amps with +5 on the gate, although Rds-on isn't guaranteed below 6 volts, and Id is only hard-spec'd at +10. At +5 on the gate, you'd be guard-banding typical data but working without guaranteed values. It's probably OK.

How much drain current do you need? The 3612 is rated for ten times the continuous drain current of the 301. I'd guess it costs a lot more too. We pay under 4 cents for FDV301's.

John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators

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