P-FET Reverse Voltage Polarity Protection Tutorial

Different ways you can protect your circuit from backwards power connections. Diodes, schottky diodes and P channel MOSFETs.

Category:

Science & Technology

Tags:

• Tutorial
• electronics
• electric
• circuit
• P-FET
• MOSFET
• Diode
• protection
• P-channel
• semiconductor
• voltage
• polarity

[R4ND0M1C]

There is any problem due to ESD?... I think that putting an MOSFET to close where the people can touch them, can distroy them due to electrostatic discharges.... Is that correct?

[Afrotechmods]

@R4ND0M1C Yes

[CoolDudeClem]

Please just answer me this one question because my head is still spinning trying to figure this out. If I was using this mosfet to turn something on or off and I was running it at 60 volts, if there was 0 volts at the gate it would be on right? But would I need something around 56 volts at the gate to turn the mosfet off? How could I put that kind of voltage at the gate if the limit it 25 volts?

[Afrotechmods]

@CoolDudeClem I implied several times in the video that if Vgs is 0V the FET would be off. It needs -4V or less to turn on. The circuit at the end of the video with the zener diode will clamp a large gate voltage down to the zener voltage.

[DracoXul]

I'm a bit new to electronic design but couldn't you use a bridge rectifier or four diodes and then it shouldn't matter which way the battery is put in, it will work?

[Afrotechmods]

@DracoXul You could do that, but then you get double the voltage drop and therefore twice the heat in all situations. Personally I think it's better to have something that just doesn't work when you plug things in backwards, then you can just flip the battery around. 99% of the time you are going to plug it in the right way around anyway.

[ftpaddict]

5:40

lol, typo

[perazaroberto2]

YOU ARE NUMBER ONE . THANK.I APPRECIATE THAT.

[cybersmythe]

The only thing I was disappointed in with this video is the fact that all the RVP I've seen in circuits have been in the form of a diode placed across the battery oriented to conduct only when the power is connected backwards. The result is a brief but brilliant light coming from the fuse when you plug the 12V in backwards. I like the MOSFET solution better, if only because it means fewer trips to the hardware store.

[n0n570p]

I think I'll just try to connect the battery sober

[VolcanicDrum]

Really nice! thank you!

[iNf3rNuSdI4bLuS1]

nice, but gotta watch it 3 more times, too much info at a time, can't process!!

[pappapaps]

wh.. what?

[SquirrelFromGradLife]

Thought about doing a video on inverters? Or do you know a really good resource on them?

[medabrundibar]

@R4ND0M1C That is, why you have to use at least the resistor in the gate, but best even the Zener, even for lower voltages then Vgsmax. That serve as a voltage limiter clamp (together with the MOSFET on-chip gate protection clamp and the gate capacitance, witch goes in nF range), so even with the ESD discharge, the gate voltage is clamped to way safe value.

[Lao999Sonnabot]

This is a good lesson, yet we still cannot make idiot proof because idiot is getting better. Electronic and Vodka won’t mix.

[SomeGuyInSandy]

Nice ;)