Why do we need gate Resistor to drive the MOSFET? How to select Gate resistor?

#foolishengineer #MOSFETdriver #gateresistor

0:00 Skip Intro
00:34 Importance of gate resistor
01:10 1. Switching speed
01:34 2. Voltage overshoot
02:00 3. Switching Loss
02:14 4. Reverse recovery of diode
03:10 5. EMI
03:34 6. Gate ringing
04:51 Gate resistor selection

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[johnruscigno]

The best way to protect the gate is to keep the mosfets as far away from my workshop as possible.

[gromosawsmiay]

great content, but one thing is missing examples how to choose proper resistor in real application.

[batica]

Definitely makes a difference having that resistor. I managed to find the value using a potentiometer and oscilloscope. Correct value drastically reduces "ringing" and makes amplified signal cleaner and stronger. I used rpi pico as a 7mhz square wave source, act244 as a mosfet driver and two parallel 12v powered bs170s as amplifiers. The resistor value varied between 220 and 370 ohms depending on mosfet load.

[dr_jaymz]

This is important stuff that people often learn the hard way. If you have a pretty beefy mosfet, gate resistance too small; mosfet goes bang. Gate resistance too large; mosfet goes bang. In both cases, often something else goes bang, like the gate driver and possibly as far back as killing the controller before that. Things really go bang when the mosfet fails as a short and its in a H-bridge or something because then you can short your extra beefy power supply and all the magic smoke comes out.

[roeloftooms]

There is another reason. To prevent a low power driver output to be blown up. The gate capacity can draw huge peak currents to charge the gate capacity when the FET is switched on. For sure with microprocessor outputs connecting to the gate it is advisable to use a resistor.

[LFTRnow]

A resistor to ground or Vdd is also wise if you want a fail-safe design. If the input to the FET gate is floating (which it is until the mosfet or driver is turned on (and running the appropriate code section), then it easily can float to turn on, partially on or off. If using a micro, it can be several ms or 100s of ms before the output pin is driven with a known state. Also, low resistor does not increase heat, fast switching does (since the average current does) and also a slowly rising and falling gate voltage will cause the fet to be in the linear (ie resistive) region too much of the time compared to the signal it is driving, that translates to efficiency losses and heat.

[DasIllu]

It took me far too long to figure out what you mean by "Dyabadeety" 😀
Also, shouldn't there be another resistor to ground to decrease depletion time in the transistor?

[beakytwitch]

Try placing a ferrite bead around the gate wire to stop ringing..

[mrmilan]

Excellent way to introduce any subject with graphical pattern.. 👍👍 This s the key of electronic. Thanks 🙏

[RinksRides]

Good job on explanation, animation, and thank you for omitting the silly background music. I can understand you clearly.

[vincentrobinette]

I will also often add a small value of resistance as close as possible to the output pin of the driver IC as well as at the gate. That helps soak up reactance in the circuit board trace, or, lead wire between the two devices. It can be a very low value, ~2.2-4.7 Ohms. I agree, the bulk of the total resistance should be at the MOSFET gate. An individual resistance should be used on each gate, if running several FET's in parallel.

[Anthonylopez-rdnr]

I did learn something new today, will treasure it for life.
Nice job
Thank you!

[pcrengnr]

Thx for sharing, however the Miller effect has the most profound effect on switching speed. What size range of resistor are you talking about 1Ω, 10Ω, 100Ω 1KΩ. It takes amperes of current to push the output fast against the Miller capacitance.
A sim or lab work would have been most helpful but you did get a click outta me.

[veerabalaji]

@Foolish_Engineer can you post video for AMBA AXI protocol

[Electronzap]

Good tips. I'll keep them in mind when I run into a MOSFET having those problems.

[jagmarc]

With resistor value too small, some microcontrollers fail to convey the output logic state. The software drives a '1', sets the register latch but the output latch stays at '0'. Because 'pulled down' by the gate capacitance.

[JeromeDemers]

I love your short content and the summarize. I would like to see real oscilloscope images Or simulation? I would assume this could be simulated if you add the other parasitic components

[liam]

Also beware of the inductance between driver and gate. It caught me out once before!

[ruwanpremashantha]

One of the best video series about mosfet. Also very interesting.

[blackarnab]

Would you please show us to calculate gate resistor without mosfet driver ic and also gate pull down resistor calculation.