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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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Mosfet testing for short from youtube repair video

In the 23:40 of the youtube video https://youtu.be/YQ7SXJqIpzs , the presenter does a p-channel mosfet test for short, using his bench power supply on the circuit. From what i understood, he ...
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P-Channel MOSFET Flipped on Schematic

I'm designing a circuit which has a bluefruit nrf52832 micro controller built into it. When referencing the schematic provided by Adafruit I noticed that they had +VBAT going to the drain of the p-...
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84 views

What are these two components ? I can't identify them

I'm having a hard time finding what these two components are.i can't find them anywhere. The first one is 3 leg MOSFET which has PDB marking on it and DD on the silkscreen The second one i can't ...
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51 views

MOSFET switching on

I have a doubt. Consider an N-MOSFET: which is the voltage that can switch on it? The voltage between Gate and? Sometimes I read "between Gate and Bulk", sometimes "between Gate and Source", sometimes ...
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68 views

Comparator loses voltage when connected to mosfet

I want to make a discharger for 18650 batteries so I can store them at a specific voltage. I built a comparator (LM393) with a voltage reference to 3.8V at the inverting input and the voltage of the ...
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2answers
69 views

Cheap alternative to limit inrush current (eg. relay bypassing a fixed resistor or MOSFET)

I'm editing the question because several (great) answers focus on the fact that the LTC3780 module (inside ajustable my power supply) can handle the inrush current (maybe, maybe not). I'm glad to know,...
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2answers
59 views

Can I do KVL around transistors? (MOSFET and BJT)

I'm having a lot of trouble with more complex transistor DC circuits (can't wait for the AC, heh). Basically, what I want to ask is does KVL holds "around" a transistor as well? For example, if I ...
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50 views

pwm RC filter question

I'm new here but been playing with electronics for a while now. I have this project where I'd need to read pwm controlled signal from mosfet. This is how stock application controls pwm valve: I want ...
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18 views

Does my PWM led circuit controlled with NodeMCU and Mosfet work properly. What should I do to improve it? How to calculate for each components?

If I understand it right, when there's is signal from ESP, the PNP and NPN be ON, and Vgs=0. If they're OFF Vgs=+12V and the LED will shine. R=1K is to limit the Ib of NPN, and R=10K is the resistor ...
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26 views

How to calculate R1 and R2,? How do Mosfet IRF540 and ESP work in the circuit

So the 3.3V PWM signal from ESP is sent through R2 to the Gate to breakthourgh the Vgs(th) to make Mosfet ON, and the author of the circuit say Gate is pulled high to 12V by R1. But I don't understand ...
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129 views

Is there any advantage to using multiple tracks in this PCB design?

I'm fairly new to PCB designing, but I'm loving experimenting with it. Currently, I'm trying to develop a simple PWM circuit using MOSFETs to control an RGBW strip, using an Arduino with an integrated ...
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38 views

Understanding Mosfet Circuit with PWM

I am wanting to control a voltage range of 0-10v across a 10k load with PWM from a micro. Now I was told to use this circuit with an n channel mosfet: This is what I understand so far: R1 is to ...
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32 views

BeagleBone Black Driving NFETs w/GPIO

In short, I want to drive some NFETs directly from some of the BBB's GPIO. 3 of the NFETs will pass 1-3 Amps of D-S current and 1 NFET will pass <1 Amp from the D-S. As you may know the BBB's ...
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2answers
48 views

trying to figure out the differences between the six transistors provided by the schematic tool [closed]

My background consists of a BS in Computer Science and an MS in Computer Science and Engineering, both from the University of Washington. My MS consisted mostly in the very high level design of a ...
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3answers
841 views

Resistor Selection to retain same brightness in LED PWM circuit

I am making a simple LED PWM brightness control circuit. I am using a relatively high power White CREE LED, N-channel Enhancement MOSFET BSS316N and Resistor R. The circuit is as shown below. I am ...
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46 views

Designing a circuit using an LT1073 DC-DC Converter

I'm currently designing a circuit to convert a 24V (±30%) to supply a 3,3V IC used to monitor currents. I need to use the LT1073 which has the following diagram. The operations of the component and ...
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43 views

Testing 8 pin P-Channel MOSFETS on Laptop Motherboard

My laptop died recently and I’m testing the motherboard. I’m led to believe these two MOFSETs on the board may be part of the issue PQ301 and PQ302. Using a multimeter continuity and diode mode; ...
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1answer
46 views

Single MOSFET current source (JFET like)

Is it possible to build MOSFET current source similar to JFET current source like this: simulate this circuit – Schematic created using CircuitLab With MOSFET it should be something like this: ...
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34 views

MOSFET working when we connect separately outside of PCB, if we solder in board, its not working, what may the problem? [closed]

MOSFET working when we connect separately outside of PCB, if we solder in board its not working, what may the problem?
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1answer
32 views

MOSFET switch, ATtiny10, Raspberry Pi

I had posted a question earlier but I was using a BJT at the time and the solution provided led me to use a MOSFET for my application instead. I switched to the FET but still unable to provide stable ...
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3answers
61 views

ON-OFF MOSFET Switch for Induction Heater

The induction heater was tested using a relay as an ON-OFF switch before and worked so i just want to focus on the MOSFET switch part of the schematic. When i tested the circuit using a MOSFET switch ...
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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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1answer
39 views

High current, high frequency IC PWM switching with MOSFETs

I'm designing a circuit for an automotive application (chassis ground) that has a number of MOSFET outputs to drive large LED arrays and smaller motors (application tends to favour non inductive modes,...
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39 views

Problem with MAX1645B test circuit?

Please consider the schematic: The MAX1645B is a level 2 battery charger. My problem is with the P-Channel MOSFETs. There are two P-Channel MOSFETs in the above circuit. From the datasheet: ...
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68 views

How do I drive a MOSFET when I have an 11.1v power-supply and an arduino [duplicate]

I am trying to use a irlb3034 as a switch to power an airsoft motor and control it with an arduino. I am using a diode between the source and the drain and a 2.2k resistor between the gate and the ...
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2answers
103 views

Using Mosfet with seperate Logic Converter and Arduino

I am trying to use an IRLB3034 with an Arduino even though it is not a logic level MOSFET. I am planning on using an LM2937 12v regulator like the schematic below: The connection going off the page ...
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2answers
59 views

Correctly using MOSFETs

I'm using a P-Channel (DMP1045UQ) and an N-Channel (BSS138K) FET to pull a 12v Logic line (12v @ 5mA) high (from GND) from a Logic Level(3.3v) MCU I/O pin. Here is the schematic, where ...
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1answer
24 views

Voltage or Current Control with a Microcontroller for Pressure Regulator

I am wanting to control the flow rate of a pressure regulator (https://www.festo.com/net/SupportPortal/Files/505126/VEAB_2018-05a_8080669g1.pdf). My idea is to control this with a PWM signal 0-5v. ...
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2answers
69 views

Forward diode characteristics not starting from zero Ampere

Why the current is not starting from zero, whats the diode characteristic when current is near zero? Reading the datasheet for N-channel 60V MOSFET, I encountered this source-drain characteristic of ...
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55 views

How to calculate gate charge time for a mosfet?

I am designing the circuit shown above using mosfet NDS355AN. MCU is 5 V. However, I have become stuck as I am unsure of how to calculate the gate charge time of the mosfet. Hence what is the formula ...
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30 views

What test points to do for a switching system measurements?

I am working on a high-performance switching system. I the old ones there was no big issue in just touching a gate with an oscilloscope probe, but this time I have high voltage and very short (5nsec) ...
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84 views

If a short circuit occured across the mosfet would anything happen in this scenario?

I am just confused about understanding a simple concept. For the following circuit: Say the blue line acts as a short for whatever reason. If the LED has a forward voltage drop of 23 V and forward ...
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53 views

IRF3205 switching problem

I bought a power mosfet(IRF3205) and tried to switch but mosfet is not behaving as I expected when gate pin is triggered it doesnt change its position. Below is how my schematic looks like, I could ...
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135 views

How to identify SMD device marked LEFBV?

I have a SOT23-3 component marked \$\underline{\textrm{L}}\,\underline{\textrm{E}}\,\overline{\textrm{F}}\,\overline{\textrm{B}}\,\textrm{V}\$ as shown in the following images: The following ...
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2answers
42 views

MOSFET Controled Relay Problem

As a way to power-on/-off a circuit load, a MCU is used to drive a relay through two MOSFETs. The problem is, when the MCU GPIO output is measured 0-volt, the relay could stay connected. Can anybody ...
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40 views

How to find the Common Mode Rejection Ratio of this circuit?

My attempt was like, by using the formula, I can get, \$CMMR=\frac{\sqrt{2\cdot4\cdot8\cdot5\cdot10^{-6}}\cdot44000\cdot2}{x}\$ For the denominator, I used both 10% and 20%, but all the finals were ...
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1answer
69 views

Constant-gm bias circuit

I am doing a study on Improvements in biasing and compensation of CMOS opamp. Do you guys know how to come up with the equation for RDS4C ?
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Mosfet not turning off when gate is grounded

I have a FQP50n10 mosfet which I used to drive an Arduino and it was working great. For the past few months I've been trying to make a circuit but it’s not working with the values I want because I’m ...
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2answers
83 views

Buck converter for Li-Ion 2s battery charger

I'm currently doing a project that requires the charging of a 2s Li-Ion battery. I have an 18V 10W solar panel that I want to charge my battery using a buck converter. Im controlling the switch and ...
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1answer
40 views

Why is SLEW RATE in nMOS amplifiers worst when the output is going from LOW to HIGH?

And, of course, why in pMOS amps the SR is worst in the other case (output going from HIGH to LOW).
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37 views

Buck Converter MOSFET Output Voltage distorted (PWM)

The input to my buck converter MOSFET switch is a PWM signal with a certain duty cycle. However, upon observing the voltage waveform of the MOSFET, the voltage is a bit distorted. The input to ...
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1answer
63 views

MOSFET Datasheet

The C2M0025120D datasheet, on page 3 (see attached picture) shows the characteristic curves of the drain-source on-state resistance Rds as a function of temperature T (on the right) and drain current ...
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1answer
42 views

DC motor & microcontroller sharing power suply: dc motor shuts off after a few seconds of running

I have the following circuit: When I close the mosfet gate (i.e. set pin 1 to high), the dc motor will run for a few seconds and unexpectedly then stop. Inspecting with a multimeter, I found that ...
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43 views

Peaks in XOR-XNOR Waveforms

I have been designing some two input XOR-XNOR circuits using Cadence Virtuoso. All of them are working as expected but there is a little problem when both the inputs make a transition; the XOR and ...
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2answers
68 views

MOSFET drain-source on-state resistance as a function of temperature and drain current

I have a question regarding an article/paper I have read (https://www.electronicdesign.com/power/analyze-mosfet-parameter-shifts-near-maximum-operating-temperature) and hope someone can help me here. ...
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1answer
53 views

Gate threshold of Mosfet [duplicate]

I am using the IRF540N. Its gate to source threshold voltage is 2v - 4V (VGS = VDS, ID = 250µA.) Does "gate to source threshold" mean I need to apply voltage above 4V to the gate? How is Id = 250uA ...
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2answers
100 views

MOSFET switching with 5V but latching ON with 12V

I am having an issue with a control signal. I have a CEP50P03 P channel trench MOSFET that is supposed to switch a 12v power supply. I am having an issue I can not figure out. When I power the ...
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45 views

Trying to come up with a overvoltage overcurrent reverse polarity protection circuit, is option 3 done right?

I´m reading for the past week about P-Channel mosfet reverse polarity protection circuits. Then I´ve found this post http://kaktuscircuits.blogspot.com/2014/07/reverse-polarity-and-overvoltage.html ...
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46 views

Testing for a bad MOSFET

I'm using a logic-level N-Channel MOSFET, specifically the FQP30N06L. It doesn't appear to work in my circuit, so I decided to attach a DMM to it for test. My test was as follows: DMM to ohm / diode ...
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MOSFET Choosing For SPWM Inverter

I'm trying to build a 220V spwm inverter with 30kHz carrier freq. with 350V input and 7A output current. I'm trying to choose suitable mosfet but I'm very confused about dv/dt, reverse recovery(body ...