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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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Single-Ended Op-Amp

For part A: Consider an increase in the voltage at Vi1 while Vi2 goes down by the same amount This will cause Iss(M7) in this case to push more current to the M1 side while the M2 side current ...
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27 views

Current Mirror - Find Acceptable Range of Vb

I'm stuck on part A - in particular finding Vb range Here's what I have so far Now, here's where I get lost I have no idea if my method is correct. I'm confident about my value for Vx but no clue ...
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38 views

Voltage and MOSFET power dissipation

I have a Brushless DC motor speed controller, operating voltage 70V and drawing a current of 10.8A (~ 756W) to attain my required speed of 2800 RPM at full load. I had to replace 2 of the 6 MOSFETs ...
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30 views

MOSFET Cascode Resistance

Hi, I'm trying to find the resistance Rx in the picture. Now, usually I would assume that (if channel length modulation is non-zero), that this would be 1/gm2 in parallel with ro2. However, I ...
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28 views

MOS Differential Pair - Transistor Mismatch

I have the following, I'm not too sure how to proceed. Usually, I can just split the circuit down the middle due to symmetry, but since there's a transistor mismatch, I can't even do that. Do I ...
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What's wrong with my1943/5200 Mosfet Amplifier? Blown on first run

I have just brought an 1943/5200 mosfet based amplifier board. Shopkeeper said it's rated for 24-0-24 AC. So I connected it with 24-0-24 transformer like this in image below. As soon as I turned the ...
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41 views

MOSFET voltage during switching

I'm simulating a 3 phase inverter of 48 V DC link which is feeding an inductive load (Brushless DC MOTOR), and I'm facing a problem that's ruining my day. Can anyone help me by explaining why ...
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46 views

BJT saturation question

For the following question, how do we find \$I_B\$ and \$I_C\$? Would it be $$I_C = \frac{V_{in}-V_{BE}}{80k}$$ and $$I_B = \frac{12-0.12}{5k}$$
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Limiting inrush current in N Channel MOSFET power switch

I have a N-MOSFET as power switch like this: I want to add a fuse on the power line but I have few capacitors on the across the load and I am worried that the inrush current might blow the fuse off....
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33 views

Powering a low current device from a mosfet N

I have a question regarding a circuit providing low current capacity voltage for device powering, that goes down from a lot higher voltage: How does it exactly work? I understand that the Q1 gate is ...
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34 views

PWM as a voltage regulator for 12V wiper motors and 14.8V LiPo

I'm using 12V (~40W) car wipers motors for small robotic project. Motors are driven over MOSFET H-bridge (IRF1405/IRF4905) with PWM speed/power regulation. Currently a voltage source for motors is a ...
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22 views

Depletion Mosfet as current source to power load

I came acros the following application note for a Depletion Mosfet (https://www.infineon.com/dgdl/Infineon-Application_Note_Applications_for_Depletion_MOSFETs-AN-v01_00-EN.pdf) and i got intrigued. ...
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34 views

LED and optocoupler MOSFET switch connected with an inductive load

I want to ask, if this circuit will work. I think the flyback from the inductive load the mosfet is connected to will break the optocoupler. The LED is connected through a resistor which should ...
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71 views

Does the lack of a primary DC blocking capacitor cause my tesla coil driver to explode?

Lately I've been tinkering with an SSTC half-bridge driver. I've ran a couple of tests using relatively low input voltages ~50V and the IGBTS seemed to do fine, there was no noticeable heating at all. ...
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98 views

AC MOSFET switching without any diodes? [Low-Cost AC Solid-State Relay With MOSFETs]

Is it possible to switch an AC load using two MOSFETs in anti-series such as the picture below? In this mode, each MOSFET is on during one half of the wave and the other's body diode conducts to ...
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level-shifting a 5V pwm signal to 10V for speed-controller using a mosfet - looking for help solving voltage drop problem.

I have tried to solve this by googling, reading datasheets and discussion. Made a bunch of breadboard designs and finally got one do what it's supposed to on the breadboard. But suffers a voltage drop ...
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Solving the MOSFET, using KVL?

The question is Find VD and ID? The FET has Vth = 1.0 V and k(w/l)= 1.0 mA/V2 and λ = 0, VDD = 5 V. My question is can I use KVL like this Vdd - R1 ID - R2 ID - R3 ID =0 rearranging for ID = 11/5? ...
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35 views

Mosfet switching

I'm implementing mosfet switching circuitry using the P channel enchancement mode mosfet DMP2305U.Where Vs = 3V and Vg is using as control voltage and toggleing between 0 and 3V . When Vg is zero ...
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30 views

Overdrive Voltage Effect on Cascode Operation

Working on this exercise: I understand that if all the transistors in a cascode have the same current and the same Vgs then they will have the same Vov. However in this case the Vgs do not seem to be ...
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34 views

Pwm DC output smoothing

I'm in the process of assembling a big 25Ah 4S (16.8 v when fully charged) battery pack. The plan is to multi-purpose that to different DC output voltages so the PWM choice felt natural. Now I want ...
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65 views

What limits the number of MOSFETs/IGBTs in Series / Parallel

I was looking at HVDC systems out of curiosity and I have a question that I have not exactly found an answer for. In HVDC converter, because of the high voltage (Tens/Hundreds of kV) they have to ...
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39 views

Common source mosfet problem

In this circuit \$I_D = K(V_{GS} - V_{TH})^2\$ and \$V_{GS} = \sqrt{I_D / K + V_{TH}}\$ But if I have neither \$I_D\$ nor \$V_{GS}\$, how can I solve this problem? One of them must be known — ...
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35 views

Buck converter MOSFET

I want to build a buck converter and step down the voltage from 100 V to 12 V. My question is: Should I use p-channel or n-channel MOSFET, and why?
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Doubt regarding dual channel MOSFET datasheet

I came across a dual channel MOSFET link for dual channel MOSFET But I am confused about the drain current of 0.63A. Do they mean drain current of each channel is 0.63A or for both channels combined?
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MOSFET W/L ratio limits: what's (un)reasonable?

The answer to this question is probably process-dependent, but what are the limits of the W/L (gate width/gate length) ratio for MOSFETs? I don't know what is in the realm of the insane. I saw a ...
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Can I chain Pwm->mosfet->(current as pwm)->mosfet->motor? [closed]

I am trying to design a drone using a microbit with 3 pwm channels. I have a Microbit microcontroller that I have been having fun tinkering with. I am thinking of see how much I can do with it, in ...
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37 views

P-Channel MOSFET not behaving as expected

I bought some IRFD9024 p-channel MOSFETs, and for some reason there seems to be a diode drop from the SOURCE to the DRAIN. As far as I understood it, the body diode is from the DRAIN to the SOURCE as ...
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1answer
57 views

How to amplify current and buffer voltage

I have a battery supplying 5V@500mAh and an LED (the load) which draws 1000mA@5V (twice the current the battery supplies per hour). I found some circuits that have NPN transistors only and other ...
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14 views

Specifying channel length of NMOS [on hold]

What is the syntax to specify channel length of a nmos in LT Spice ?
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44 views

MOSFET Differential Amplifier voltages via PSpice and by hand

I want to do an analysis on a differential pair and there is a problem when the pair is in common-mode, at least that's what PSpice says. I find that \$V_{DS}\$ of both MOSFETs is 1.1V and PSpice ...
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MOSFET switching speed

I´ll be clear and fast in what I´m asking once my last question did not have many views. So, a couple days ago I was at the bench switching a IRLZ34N with a 555 timer, powered by a 15V, @ 50kHz, \$33\...
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0-5 to 0-12 volt level shifter at high frequency

what is the best way to shift PWM at 500kHZ from logic level 0-5 volt to 0-12 volt to drive a mosfet? answers here were no good they only work for lower frequency and pwm is distorted at 500kHZ ...
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Triode and saturation region in mosfet

What is the difference between the triode ( ohmic ) region and the saturation ( linear ) region in mosfet ?? It's confusing since both regions are linear but why does mosfet work as an amplifier in ...
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38 views

Is Adafruit's recommendation for led strip driver MOSFET incorrect?

Adafruit's article ( https://learn.adafruit.com/rgb-led-strips/usage ) states that transistor IRLB8721 can be used with 3.3V or 5V gate voltage to drive LED strip. However, in IRLB8721 datasheet ( ...
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Mosfets heat up in a BLDC controller

I am trying to build a bldc controller. I have the following schematic I should mention that for the gate drivers I used ir2101 ICs. Everything works fine but when I connect the motor (350w ...
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55 views

How to turn on high-side MOSFET of a buck converter

I'm trying to simulate some buck converters with real MOSFETs instead of ideal switches. The problem is that I don't know exactly how to properly turn on the transistor. The simple buck converter ...
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60 views

Voltage control

I've been trying to design a control circuit to switch supply. What I want to achieve? I need 24V voltage for supplying an ultrasound sensor. There are two ways of gaining 24V: ...
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39 views

IRFZ34N doesn´t switch on when a NE555 timer pulse is applied

simulate this circuit – Schematic created using CircuitLab I have the above circuit in my breadboard. The problem in a nutshell is that when the NE555 timer is switching at 50kHz in astable ...
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37 views

Why does my GPIO only show 2V when connected to the Gate Termina lof NTE2390?

I've got a circuit set up with a motor that matches this diagram. When a 3 V power supply is connected to the Gate terminal, the motor spins. However, when I replace the 3V supply at the Gate ...
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2answers
34 views

Calculating Gate Resistor for IRFP260N [closed]

I want to use two IRFP260N for DIY Inverter 12-220V. I have CD4047 and I want to use it as driver. What resistor value can I put between CD4047 and IRFP260N Gate?
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Is the MOSFET NTE2390 broken if connecting only source and drain powers a motor?

I've got a small motor wired to the drain of an NTE2390, with the other end of the motor hooked up to ground. When I connect to the source of the MOSFET to power, the motor starts turning even though ...
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26 views

Measuring MOSFET Voltages not adding up. Vgs /= GNDs - GNDg

I am measuring a power mosfet with a multimeter. The voltage at the source with respect to GND is ~291V. The voltage at the drain with respect to GND is ~16V. The P-type mosfet is rated for 250V, so I'...
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2answers
33 views

Current pulsing circuit, troubleshooting

I was not sure what to title this question. What I have two version of the following circuit, that I have built and modelled. The application is to create a pulsed magnetic field, by pulsing a ...
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ngspice .measure syntax in AC + par()

Why do the two netlists give totally different output impedance values ? Netlist 1: ...
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1answer
34 views

What is the parasitic resistance due to an IC package in a mosfet? (or any package)

How much resistance does the package of an IC contribute to the paraistic resitance of a circuit? (most applicable to mosfets)
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64 views

Controlling an output based on level of AC signal

This is my first post on this StackExchange after years of lurking, so please be gentle! I would like to be able to enable an output (for example an LED) based upon an AC voltage from a split-core ...
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97 views

High side MOSFET problem

I have built a high side MOSFET driver and hooked it to an atmega328p. Having an issue with the setup, the MOSFET is not switching on completely due to the low Vgs. For this circuit the expected Vgs ...
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67 views

Bootstrap mosfet driver with ir2101

I am trying to build this circuit but I don't know how to test it. When I am measuring the voltage on the gate of high side mos is almost 12 volt like VCC. So to speak .. the boostrap circuit isn't ...
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Why the mosfet's gate resistor show this current consumption?

Here is my H-bridge circuit. and here is the graph of the current of R1, with LTSpice My calculation for the bases of the pnp & npn Vsupply -((Vbase Q3 - Vbe) / R5) x R3) 24V -(((3V3 - 0.65)/...
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18 views

Blocking voltage and breakdown voltage

Is there a difference between the blocking voltage and the.breakdown.voltage in mosfet transistor ? Or the two are the same?