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17 votes
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Why can't an MCU's GPIO pins directly control power MOSFETs?

Sometimes they can. But when they can't there are two main reasons- not enough voltage and/or not enough current. The voltage is required to get many MOSFETs to turn on so they have low resistance. ...
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10 votes

Is reverse polarity protection this simple?

For the case of a well regulated 12V input powering a single resistor, then yes. But, generally no. If your 12V source might ever have spikes (perhaps at plug in time) that exceed the (usually 20V) ...
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10 votes

Why can't an MCU's GPIO pins directly control power MOSFETs?

The MOSFET gate turn-on voltage may be higher than what an MCU I/O pin can provide. A driver circuit can translate the I/O logic output voltage into a strong 'on' gate voltage. A MOSFET drive circuit ...
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9 votes
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What is the use of a P-channel FET on a power line?

The FET is there for reverse polarity protection. When the power is first applied, since the FET's source node doesn't know what voltage it has, the FET remains off for a moment. The body diode is ...
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7 votes

Why can't an MCU's GPIO pins directly control power MOSFETs?

Because they are electrically incompatible. If you have a MCU with 3.3V IO voltage, it is possble that N-FET requires more than 3.3V at gate to turn on properly. If you have a P-FET and the supply at ...
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5 votes
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How is a highside gate powered with a bootstrap circuit and MOSFET driver?

It won't work as shown on the schematic in your question. The two wires to the load have to be one wire. I've fixed it below: The driver turns on the bottom FET using its own +12V power supply. The ...
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5 votes
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Why use N-channel and P-channel MOSFETS with an ESC instead of just using N-ch MOSFETS?

Several things: As winny commented, it can be easier to do. And at low-ish power levels and low frequencies (a motor's going to run max ~kHz?), the poorer performance of PMOS isn't so significant. ...
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  • 3,052
5 votes

Where do you find how much heat a heatsink is rated for?

A heatsink from a reputable supplier will have a datasheet that tells you the degC per watt. I don't blame you for wanting to use a cheap one without a datasheet, but your options for that are ...
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  • 4,903
5 votes
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Why is this on resistance so high on P10NK70ZFP MOSFET?

Your test is not perfect, the parts are specified with more like 3-4V Vds, but, yeah, you got some counterfeit parts there.
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4 votes
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Using dual output LDO

No, you cannot connect the outputs of the AP7346D directly even if you only enable one at a time. They each have an internal discharge transistor that is enabled whenever the output is disabled, and ...
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4 votes

Is reverse polarity protection this simple?

Almost. To make these somewhat reliable you need a bit more refinement. Some protection in the form of a zener diode protecting the Vgs is required. The are lots of application notes on this, for ...
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  • 1,680
4 votes

What voltage will drive this MOSFET best?

The gate needs enough current to fill its capacitance fast enough to get you out of the linear region before dissipating too much power. Yes, but I am more likely to look at figure 1 on that same ...
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  • 7,307
4 votes
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How do you disconnect a circuit briefly when a button is pressed?

This is probably more like what you need: - simulate this circuit – Schematic created using CircuitLab Regarding your circuit posted: - 1 volt won't turn an LED on and it'll be barely enough ...
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  • 385k
4 votes

Will this voltage divider keep my MOSFET on?

I feel I should first address something you already know, which is that your circuit will kill you if you so much as look at it the wrong way. You will have to take several precautions, such as ...
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  • 8,348
3 votes

Are SMPS (inductor) current limits mostly thermal?

As with all components, an inductor has several limits, and you have to stay within them all. The inductor has a saturation current limit, above which the inductor value quickly drops, to possibly 1/...
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  • 142k
3 votes

Bi-directional current source based on MOSFET or IGBT

my target is to switch on/off a 10mH inductive load with 3.5A in an extremely short time (<50us), the inductive load will generate a large emf inverse voltage due to large dI/dt. When "...
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  • 385k
3 votes

Need help identifying SMD IC

Function and pinout matches TPS560430Y, but there may be others with this pinout. The inductor 2.2 µH is a bit small for this circuit, but OK if used with <= 12 V input.
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  • 2,251
3 votes

Why don't inverters use BJTs to easily produce a pure sine wave?

The overarching concern is efficiency. To avoid significant losses you would prefer to have no current with full voltage across the collector and emitter (transistor off), or full current and no ...
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3 votes

Discharge lithium ion battery to a specific capacity

A Lithium Ion battery has a very flat discharge curve which makes it difficult to determine the state of charge from voltage. The voltage drop "signal" is swamped by the internal resistance ...
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  • 7,848
2 votes

Is reverse polarity protection this simple?

A single diode would suffice for reverse-polarity protection.
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  • 10.5k
2 votes

MOSFET Driver Base and Gate resistors and other input stage for PWM motor control

Choose the switching frequency, for a motor it doesn't need to be very high. Choose the switching time to be slow enough to avoid sharp edges which will make a lot of interference, but not too slow or ...
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  • 60.1k
2 votes

Is reverse polarity protection this simple?

As others have said, your circuit would work for reverse protection under ideal conditions, but might not work under real world conditions. For real conditions, an ideal diode IC (such as the Analog ...
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  • 61
2 votes

Replacing a dual N-channel MOSFET with another with different heat dissipation pads assignment

Your main focus should be on comparing how the new device might perform in your target circuit and not in comparing data sheets. For instance, if your gate drivers are a tad weak (but OK for the 82100)...
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  • 385k
2 votes
Accepted

How do MOSFETs in 300-500A ESCs handle the current?

Well, MOSFETs have a special property (you can't do that with BJTs). You can parallel them. It's not unusual to see 5-10 or more MOSFETs in parallel for each branch of the bridges. However there are ...
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2 votes

How does a bootstrap capacitor power the gate?

Bootstrap capacitor is charged via diode and Q2. When the low transistor Q2 is turned on by PWM2, the SW/HS node with bootstrap cap negative is connected to ground. Then current will flow from VDD ...
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  • 90k
2 votes

How is a highside gate powered with a bootstrap circuit and MOSFET driver?

\$V_B\$ will rise towards 410 volts each time the bottom MOSFET turns off and the top MOSFET just starts to turn on. This lifts the output voltage up and turns the top MOSFET on fully and within a ...
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  • 385k
2 votes

Short circuit broke a P-channel MOSFET

If you place a 10mF cap (the one in the upper right corner) on the p-mos drain, I would imagine that the inrush current while the cap is charging is what broke the MOSFET. That is, the cap is now ...
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  • 14.2k
2 votes

Relays or MOSFETs

(I´ve been told that MOSFETs amplify current signal) Not true. MOSFETs do not amplify current. However, a buck DC converter, often implemented with MOSFETs, can output more current than is input. As ...
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  • 142k
2 votes
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Peak switching power in MOSFET as seen in LTSpice, and reduction using snubber or gate resistor

but I'd like some confirmation that these transients might be ignored. Absolutely not. They cannot be ignored but, you can easily check to see if the device you have chosen is suitable. Open the data ...
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  • 385k
2 votes

Peak switching power in MOSFET as seen in LTSpice, and reduction using snubber or gate resistor

Yes, this is a fine way to do it, given all the usual caveats of power electronics design, including accounting for stray inductance of the switching loop, peak and average power dissipation, thermal ...
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  • 3,052

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