Questions tagged [gate-driving]

Interfacing between control signals and power switches, like MOSFETs and IGBTs; charging the gate capacitor of a transistor to the voltage required to make it switch while supplying enough current to make it switch at the required speed.

Recommended reading:

Microchip application note AN786: Driving Power MOSFETs in High-Current, Switch Mode Regulators

TI application note SLUA618: Fundamentals of MOSFET and IGBT Gate Driver Circuits

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Designing a *linear* MOSFET driver stage

I'm looking for a MOSFET driver circuit that can be placed between an op-amp and a power MOSFET to operate the transistor as a linear amplifier (as opposed to a switch). Background I'm developing an electronic load circuit that must be able to step…
scanny
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Criteria behind selecting pwm frequency for speed control of a dc motor?

I'm working on a speed control circuit for a brushed dc motor (24v, 500rpm, 2A, 4kgcm). The main components that I plan to use are PIC16f873, 4n25 optocoupler, IRFZ44N MOSFET, BY 500 - 800 diode(for free wheeling). What is the criteria behind…
raforanz
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Why have both: BJT and FET transistors on IC output?

This is the structure of FAN3100 gate driver IC: (taken from its datasheet ) As you can see - there are two ouput switches: CMOS and BJT. Why they put them both?
Roman Matveev
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Bootstrap circuit for high-side MOSFET driver

I am very familiar with the operation of bootstrap drivers on MOSFET driver ICs for switching an N-channel high-side MOSFET. The basic operation is covered exhaustively on this site and others. What I don't understand is the high-side driver…
Dan Laks
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What is MOSFET gate drive capability and why do I care about it?

Someone told me that this circuit has "poor gate drive capability": simulate this circuit – Schematic created using CircuitLab What exactly does that mean? I tested it with an LED as a load for M1, and the microcontroller is able to turn it on and…
Phil Frost
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Is it okay to use a MOSFET in its resistive region with a heat sink?

Using transistors in with limited gate (or base) voltage will make them limit current, which will introduce a significant voltage drop across the transistor, causing it to dissipate energy. This is considered bad, wasting energy and shortening the…
piojo
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What is the difference between driving a MOSFET gate and an IGBT gate?

Can I use an suitable IGBT gate driver for driving the MOSFET, and vice versa? Which parameters (threshold, plateau, and turn on voltage ratings, gate capacitance, etc) must be the same for this compatibility? What are the essential differences…
hkBattousai
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How can I slow down the switch time of a MOSFET?

I have an NMOS that is switching too fast for my application. Into the gate I am sending a logic-level square wave (PWM). Unfortunately for me, as expected, the output is also a near square wave. How can I get the Vout to be more trapezoidal? Or…
hassan789
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How does this PNP transistor improve the switching performance of MOSFET?

My guess is PNP transistor might ensure fast turn off by shunting the gate capacitance (ie, when diode is reverse biased and the PNP is on.) Additional questions: Why is the gate current limiting resistance not present? What is the role of R1 in Fig…
Dynamic_equilibrium
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Paralleling MOSFETs: Can I use a common gate resistor, or do I have to use a separate one for each MOSFET?

When calculating gate resistor for a single mosfet, first I model the circuit as a series RLC circuit. Where, R is the gate resistor to be calculated. L is the trace inductance between the MOSFET gate and the output of the MOSFET driver. C is the…
hkBattousai
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How necessary are gate resistors for MOSFET gate driving?

I've been studying MOSFET gate driving recently, aiming to understand the importance of layout. To investigate this, I designed a PCB as shown below: In this PCB, I used the FD6288T ( https://static.qingshow.net/fortiortech/file/1597746029372.pdf )…
0x1a551e2
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Should I gate SCRs on when reverse-biased?

I've been told that it's a bad idea to gate SCRs on when reverse-biased. Is that accurate? I'm reasonably confident that the SCRs won't actually conduct reverse-biased whether gated or not; are there circumstances where that is not true? Are there…
Stephen Collings
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Bootstrap circuit function

I have some question about the bootstrap capacitor on a gate driver. First, the bootstrap capacitor is used because the voltage on the high-side driver's gate needs to be about 10-15 V higher than the voltage on its drain. However, if my input…
sean900911
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Using a miniature BNC connector on a PCB to measure high-frequency content with an oscilloscope

I am a power electronics engineer in R&D and often measure fast switching waveforms, specifically high bandwidth MOSFET gate signals. When connecting oscilloscope probes in the past I have found that the ground clip often induces unwanted HF content…
Jono Moran
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How important is the gate threshold voltage on a MOSFET?

I am using several MOSFETs (STP16NF06 datasheet here ) controlled by a shift register (74HC595 datasheet here ) which is controlled by a microcontoller. The spec sheet says the gate threshold voltage is between 2 V and 4 V. When controlling directly…
John Petrak
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