Questions tagged [mosfet]

An transconductance (using voltage to control current) electronic component used for switching and amplification. Acronym for Metal-Oxide-Semiconductor Field-Effect Transistor. (from http://en.wikipedia.org/wiki/Transistor)

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16
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3answers
7k views

How many MOSFETs can we safely parallel in condition of very high currents? I had problems with a motor application at 48V 1600A

I tried with some configurations in which 16+16 MOSfets of 240A each (really they are case limited to 80-90A because of source terminal, but i doubled this termminal with a very thick copper wire for ...
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3answers
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Why are BJTs common in output stages of power amplifiers?

From my understanding, the role of the output stage is to decrease the output impedance to almost 0. For that, MOSFETs seem better suited since they've got way lower \$R_{ds}\$. Yet I see quite often ...
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4answers
7k views

Driving highly inductive loads destroys mosfet driver

Background I am attempting to generate some relatively high voltages (>200KV) using a system of ignition coils. This question deals with a single stage of this system which we are attempting to ...
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2answers
3k views

Why do BLDC motor (1 kW) controllers have so many MOSFETs?

I have a 1 kW three-phase BLDC motor from China, and I was developing the controller myself. At 48 Vdc, the maximum current should be about 25 Amps and a peak current of 50 Amps for short durations. ...
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5answers
35k views

Source vs Drain polarity for MOSFETS

When using MOSTEFS as a switch I always see the drain connected to the higher potential and and the load and the Source is always connected to ground. Can you switch those so that the Source pin ...
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3answers
25k views

Do MOSFETs usually burn open or closed?

I was wondering if a power MOSFET fails due to overheating, will it usually burn as an open-circuit or short-circuit? Also, does over-temp damage usually cause the gate oxide to blow through as a low ...
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29k views

Is there a popular small signal PFET equivalent to NFETs 2N7000 or BS170?

Some days ago I was considering using a small signal P-Channel MOSFET in a design of mine, but could not find a suitable part. The specs I was looking for were something like the following: \$I_D = -...
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3answers
5k views

Why doesn't LTSpice predict this op-amp oscillation?

I'm developing a circuit to act as an electronic load for bench testing power supplies. An earlier question about how to test this circuit received several very useful answers and can be found here: ...
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5answers
8k views

Why are discrete four-terminal MOSFETs so hard to find?

I know that a MOSFET is a four-terminal device, but nearly every discrete MOSFET you can buy has its bulk/body/substrate internally connected to the source. Why is this? It makes it inconvenient to ...
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2answers
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How to design the gate resistor value?

This is the datasheet of the driver IC I am working on (LM5112). Following is the application diagram of the module. Basically this is the GATE driver circuit for the MOSFET with PDM signal as the ...
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2k views

Is it good practice to run large amounts of current through a MOSFET?

I have been looking for a good way to control the flow of a lot of current in my project. This may at some points be 40-50 amperes at 12-15 V. While relays are a good choice, they are mechanical ...
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6answers
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My MOSFET operated solenoid circuit destroys my Arduino inputs

I made a series of PCBs to power some solenoid valves that use an external power supply. I switch them with BS170 MOSFETs using an Arduino as gate signal. I based it a solution by Jason S. This is an ...
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4answers
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How can I sense the motor's current?

I need to drive a DC motor @ 24V, 6A with a MOSFET. How can I sense the current that the motor is drawing with a microcontroller? I have to know when the motor is stalled.
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What to look for in the datasheet when choosing a MOSFET?

I thought that choosing the right MOSFET for my LED strip would be easy until I discovered how many different models there are. Basically I want a MOSFET that allows me to control with PWM a 12V 6A (...
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3answers
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How can I measure gate capacitance?

Is there an effective way to directly measure the gate capacitance of a power MOSFET, like say the IRF530N? The way my circuit is behaving would indicate that the effective gate capacitance is ...
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2answers
3k views

IGBT vs. Power MOSFET for switching applications. Where to draw the line?

For lower breakdown voltages, a power MOSFET is clearly the device to go for, in view of its higher efficiency, higher commutation speed and lower price. Where should the line be drawn, upwards of ...
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2answers
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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 ...
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3answers
10k views

Why are flip-flops usually triggered on the rising edge of the clock?

Usually in digital design, we deal with flip-flops that are triggered on a 0-to-1 clock signal transition (positive-edge triggered) as opposed to on a 1-to-0 transition (negative-edge triggered). I ...
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2answers
48k views

Explain in layman's terms Vgs and Vgs(th) of MOSFET's

I'm trying to understand \$V_{GS}\$ of MOSFET transistor. From what I understand \$V_{GS}\$ normally stands for voltage gate to source breakdown, but other than that I lack an understanding. \$V_{GS(...
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5answers
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How tight can I mount a TO-220 to a bus bar?

I'm building a small switching circuit consisting of 8 MOSFETs (bi-directional blocking, 4 in each direction), which should switch 100-200A at about 1kHz. I've concluded that since PCB with a thick ...
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4answers
32k views

For 3.3V microprocessors, what's the best way to power the gate of a MOSFET?

The new processors are all 3.3V and dropping. So while I am used to 5V arduinos being able to power the gate of a MOSFET, at least most of the way, this is not going to be true any more. And for an ...
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3answers
8k views

How should I understand the intrinsic body diode inside a MOSFET?

I know there is an intrinsic body diode inside all the MOSFETs, but I'm confused about the reason why it's there. I've searched the articles but can't find a good explanation for it. Can anyone use ...
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12k views

Driving DC motors with MOSFETs and a microcontroller?

I'm developing a nano quadcopter using an Atmega328 microcontroller, powered at 3.3V, and very small brushed DC motors. The average current used by these motors is about 800mA @ 3.7V. Initially, to ...
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3answers
106k views

MOSFET as a switch?

In the picture shown, can "Output" be controlled to be 0V or 12V based on "Control"? Will be Drain and Source the way it is connected be a problem?
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Help using MOSFET to switch on/off IC

I am trying to use the following MOSFET (N-Channel) to turn an IC on and off. http://www.diodes.com/datasheets/ZXMS6004FF.pdf In my test circuit I connected 5VDC to the drain of the MOSFET and then ...
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Is this a good design for MOSFET H-Bridge?

I have been looking around trying to design a simple but working H-Bridge for an RC car motor (12V and 2~3A). This bridge will be driven from a microcontroller and need to be fast to support PWM. So ...
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2answers
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Why are BJTs more reliable than MOSFETs under severe weather conditions?

I read in a textbook (Microelectronic Circuits by Sedra and Smith, pg. 494, (2010) sixth edition) that BJTs are preferred by the automotive industry due to their reliability under severe weather ...
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3answers
10k views

Voltage spikes when driving DC motor with N-channel MOSFET

I'm trying to drive a DC motor (12V, 100W) with MOSFET IRFP054N. PWM frequency is 25 kHz. Here's the schematic: I know DSEI120-12A is not the best diode for this but I don't have any better right now....
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2answers
45k views

Gate Capacitance and Miller Capacitance on the MOSFET

How is the Gate capacitance and the Miller capacitance modeled for a MOSFET. What is the behavior for both when a Gate Voltage is applied?
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1answer
4k views

How is this circuit for level converting (5V<>3.3V) working?

Does anybody know, how is this circuit exactly working? It is level converter between 5V and 3.3V logic and it is bi-directional. I have some theory, but I am not sure with it (I never worked with ...
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5answers
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High Voltage PWM Motor Controller - Mosfets Explode

I've searched every post for an answer to this problem. I've built a motor controller circuit as shown in this diagram. I made the diagram as accurate as possible. The diodes on the mosfets were ...
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1answer
70k views

High side driver and Low side driver [closed]

Can anybody help me understand, what exactly a high side and low side driver is? In which scenario would either of them be used?
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1answer
25k views

Basic p type MOSFET question

With an N type MOSFET you let the current flow from the drain through the source when a high enough voltage is applied to the gate. With a P type MOSFET which direction is the current meant to flow? ...
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3answers
8k views

BJTs versus (MOS)FET to switch a load from a microcontroller

I would like to know what are the reasons for choosing bipolar junction transistor (BJT) versus a field-effect transistor (FET) (MOSFET or a JFET) to switch a load from a microcontroller. In our ...
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1answer
47k views

How to control a 12V solenoid valve with a mosfet?

I'm trying to control a 12V DC solenoid valve through a MOSFET (BS170), which receives its control signal (5V) from an Arduino microcontroller. This is the basic schematic: When I test the MOSFET, ...
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2answers
24k views

P-Channel MOSFET high side switch

I am trying to reduce the power dissipation of a P-Channel MOSFET high side switch. So my question is: is there any way in which this circuit can be modified so that the P-Channel MOSFET will ...
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2answers
4k views

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 ...
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2answers
4k views

What is the purpose of using MOSFET instead of free-wheeling diode in Buck topology?

(Source) I usually see Buck circuit models in which a MOSFET is used instead of a free-wheeling diode. What I understand from the Buck topology is, when the upper MOSFET is off, it doesn't matter ...
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2answers
7k views

Using a microcontroller to turn on LED strip

I have 60 leds that came in a led strip. One meter length of the led strip requires the following: 400 milliamps 12 volts I want to control these LEDs with micro controller. I'm thinking of using a ...
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7answers
9k views

Is there any reason to use junction or Darlington transistors for power applications?

In quite a few Arduino examples, you see people using junction transistors to power a motor. In this case, for example, he's using a Darlington transistor: http://www.instructables.com/id/Use-Arduino-...
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What is the difference between CPU transistors and generic ones?

Recently I had to build a h-bridge driver for my project, wireless power transmission. I learnt that I needed to have dead-time in my PWM signal given to IR2110, which doesn't have any dead-time ...
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4answers
32k views

How to reduce MOSFET turn-off delay

The title says it all in signal switching applications - besides choosing a different device, how can I reduce the turn-off delay of (N-channel) MOSFETs? Is there something similar to the Baker Clamp ...
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2answers
32k views

Determine MOSFET switching speed

How can I determine the switching speed of a MOSFET, with given Qg (gate charge), Vgs (G-S junction voltage) and gate resistor ? How should I determine the required value of the gate resistor?
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5answers
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MOSFET broke after attaching capacitor bank

I have a solenoid that has a coil resistance of \$0.3\Omega\$ and accelerates a steel projectile here. I've posted the schematics below. Normal Version that acts as a control The GPIO8 goes to 5V to ...
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2answers
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MOSFET construction

I've just read an application note and I was confused about this sentence: "Engineers often think of a MOSFET as a single power transistor, but it is a collection of thousands of tiny power FET cells ...
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Are MOSFET drains ESD sensitive?

There's a lot of post on here about MOSFETs and ESD sensitivity. But whenever the general question is asked, people always go straight to the gate and how sensitive it is. I've developed an LED ...
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4answers
12k views

Why does this Bridge Rectifier claim to have no [Diode] Forward Voltage drop

I was, "OK, this is feasible"... But then I traced how it worked and it simply blocked current through Drain and Source when a P and N pair are reverse biased; then when the other P and N pair are ...
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2answers
327 views

How to ensure my device is safe for every day use?

I have put together a simple wake up light. It has an external powersupply, at the moment rated 7V and 600mA. Inside it has Arduino and bunch of LEDs controlled by a MOSFET. It works fine at the ...
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4answers
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Don Lancaster's Magic Sinewaves

For several years now Don Lancaster is promoting magic sinewaves. They are strings of binary digits (like 420 bits for a full sine cycle) that, when used to drive a digital switch (MOSFET/IGBP), ...
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2answers
15k views

Drive a 4.8V servo signal line using 3.3V

I have a servo with an operating voltage of 4.8V. I want to drive the servo from a MCU running on 3.3V. I haven't tried it yet, but was wondering if I needed to drive the signal line to 4.8V using a ...

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