Fets for dumbies

mctrivia

I don't really know how fets work but I am looking to switch 3.3V @ 1A using a digital 3.3V signal with least possible loss. I know Fets are the way to go because I have used a FDN306P in conjunction with a LTC4412ES6#TRMPBF and get almost no loss at all. Can I just replace the LTC4412ES6#TRMPBF and run the gate of the fet from a pin on the prop to switch a load?

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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.

Mike Green

You need to learn how FETs work if you're going to use them.

MOSFETs are voltage sensitive devices.· They need a certain amount of voltage on the gate (relative to the source lead) for them to turn on and the amount of current they conduct depends on the voltage.· Most MOSFETs require a bunch more than 3V to conduct any significant amount of current.· There are graphs on the datasheet that show you how much.· You need to use a MOSFET that will turn on with a 3V applied gate voltage or you need some kind of MOSFET driver that will make more voltage available.

DavidM

Hi mctrivia,

I use these two with the prop

ZVP2106A Logic gate drive, 60V 280ma TO92 P Channel
ZVN2106A Logic gate drive, 60V 280ma TO92 N Channel

There's also this one..

NTD3055L104 12amos 60 VOLTS LOGIC LEVEL DPAK ( But I haven't tried this one yet)

regards

Dave M

mctrivia

so if I am reading it correct connecting the source to 3.3v and the drain to the positive side of my led will cause it to light if a logic 0 is applied to the gate because the Vgs would be -3.3V? i can not find any example schematics were the load is between the mosfet and ground.

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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.

pacman

Can someone point me to some schematics for 'propper' use of a fet as a high current (1A, 12VDC) output driver, directly coupled to a Propeller output pin ? - Efectively as a relay replacement.

I've had a good search and have not been able to find anything I can undestand.

Thanks in advance.

Paul