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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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Half H-bridge using only ntype mosfets or npn transistors

Would the following circuits work? I keep thinking I need a mixture of ptype and ntype mosfet or npn and pnp transistor for a half h-bridge, but I keep seeing schematics with only ntype mosfets or npn ...
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31 views

KVL Issue - Telescopic Casocde Amplifier

Hi, my question is regarding the equation circled in red in the highlighted text above. I can't seem to understand the reasoning behind why all the transistors are included in that equation. My ...
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33 views

active pfc circuit

I have come up with a bridgeless active pfc circuit. Does this arrangement make sense? When M1 and M2 are on, the inductor current ramps up until M1 and M2 are turned off. No current flows through ...
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42 views

Switch for low voltage, high current Shape Memory wire

I need a switch to allow current to pass through a wire to Joule heat it. This is a nickel-titanium wire (Shape Memory Alloy, SMA) which has been programmed to bend into a particular shape when heated....
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84 views

Mosfet \$\mathrm{V_{GS}}\$ not in datasheet

I have a datasheet for a MOSFET but can't find the \$\mathrm{V_{GS}}\$ to get the rated \$\mathrm{R_{DS(on)}}\$. It only shows the \$\mathrm{V_{GS}}\$ maximum rating which is the usual ±20V. The \$\...
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22 views

Loading an AC generator with DC Chopper + resistor

We're in kind of a bind at work and looking for easiest / cheapest way to load an AC generator (Synchronous permanent magnet machine). We have access to a big 300A Mosfet module along with it's ...
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45 views

the difference between K coefficient and gm in the mosfet

i know that K in mosfet is as beta in Bjt but since it represents the change in Id in relative to the change in Vgs isn't it supposed to be the transconductance gm ? but why is it different and the ...
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50 views

PWM Not Driving IRL520N MOSFET

I am trying to switch a IRL520N logic-level MOSFET using a 0-5V PWM signal from my microcontroller (PyCom FiPy). I tested just the MOSFET with a 10 Ohm series gate resistor and my load is a 9-15V ...
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58 views

Why does a virtual ground form for differential pair?

In the schematic above for MOS differential pair, why does virtual ground form? The book says because of symmetry, but I don't really understand it.
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226 views

Parallel Power Supplies with Ideal Diodes

I'm working on a project that operates at 5v - and can draw UP to 10 amps. Under normal conditions, it won't be doing that - probably closer to 3 amps, and (if configured for low-power) only 450mA or ...
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29 views

Is the same send a pulse with 5V than reduce voltage with driver? [on hold]

I've a conceptual question: if I send a PWM to a MOSFET that drives a Motor with 5V, is the same than using a driver to send from 5 to 0V? For example and be clearer, is the same send a %50 duty ...
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72 views

How to detect whether a solenoid is actually attached to a MOSFET?

An injector is usually switched to ground to turn it on using a an N channel Mosfet. But how does the MCU knows when this is disconnected? I'm trying to drive a solenoid, but if the solenoid is ...
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70 views

Power ORing using P-Channel MOSFETs

We have a control unit used in marine applications running of 12V nominal voltage with a current consumption of about 1A. Today we are using a P-Channel MOSFET with some added circuitry (Zener, ...
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90 views

MOSFET logic gates: Putting the pieces together

So I got this problem. And I know MOSFETs...Sort of. So the area in red is a NAND gate and the area in blue is an Inverter...I think? So I know what those two pieces are, now how do those connect? ...
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42 views

Dysfunctional IRF9540

simulate this circuit – Schematic created using CircuitLab I am trying to build my own SMPS and I was intending on using a P-Channel MOSFET for high side driving the main circuit. The MOSFET in ...
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25 views

Serial communication between uC and SIM800 is generating unwanted current consumption

I am using the IRFZ44N to turning on and off a SIM800 module, at the other side there is a micro controller that enters to a low consumption mode in order to save energy, the SIM800 module looks to be ...
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31 views

Fully Differential Amplifiers - Why does M3 drop to linear region?

From http://www.ece.tamu.edu/~spalermo/ecen474/lecture17_ee474_fully_diff_amps_cmfb.pdf I'm having some trouble understanding why M3 drops to linear region. First Question - The increase in Ib ...
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66 views

Looking for a motherboard CPU Power MOSFET replacement - is this OK to put not exact the same?

I have a motherboard with broken PDC3094X (Potens Semiconductor) in VRM circuit. I cannot find the replacement with exact same parameters and the original part is impossible to get. I don't have a lot ...
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21 views

Transceiver IC SN74LV245A at different voltage levels pull up resistor require for current improvement

I've gone through datasheet of IC Page number 12 Figure 5 shows typical application of IC which is 5 to 3.3V compatibility. In my design My sensor Output is 1.5V to 2.2V so we're planning to have ...
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22 views

Arduino PWM & MOSFET successfully control LED but not electromagnet? [duplicate]

I've got an Arduino circuit set-up so I can control the strength of an electromagnet using a potentiometer. My potentiometer is hooked to A0, and I'm mapping its value to PWM pin 3 which then goes to ...
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65 views

If I need to find an MOSFET spice model with a particular length and width, where do I start?

I was using a 180nm NMOS and PMOS but now need to use an NMOS with about L=.36u and W=100u. I have two models but I dont think I can just change the length and width to any value. How can I check if ...
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116 views

Arduino PWM successfully controls LED brightness but not electromagnet strength? [closed]

I'm trying control the strength of an electromagnet using an Arduino. I've included my circuit (sorry it's a Fritzing diagram, I'm working on the schematic and will update once it's ready) and code ...
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45 views

Calculate the junction temperature of a MOSFET during pulse

Hi all I have a question regarding using a MOSFET for a constant current source. I have found this question with some answers but it wasn't clear to me yet. I want to create a constant current LED ...
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4answers
78 views

Will switching a LED on and off at a said frequency reduce or increase heat loss?

In my case, a 50W 34V LED is being used to light a small box. To reduce heat generated by the LED, we are switching it on and off at 50Hz. But I was wondering will this actually help? In the case of ...
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66 views

TO-220 MOSFET (or SS relay) for 24VDC with 0V turn on voltage

I am in need of a MOSFET (or solid state relay) in a TO-220 package that will switch 24 VDC high side to an inductive load (up to 2 amps) when 0VDC is applied to the gate. I don't even know where to ...
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65 views

Mosfet: gate voltage 0 but still led strip on

LED strip: DC, 4W Mosfet: IRF740 (datasheet) To Do: Use wall socket (AC) to run DC led strip and also turn it on/off with MOSFET and arduino. AC to DC is done with rectifier and transformer. So ...
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2answers
76 views

Fixing conmutation for high voltage switching with power MOSFET

I have an issue with a charge circuit for a capacitor as load. I want to switch approximately 400 V DC to charge a 1000 µF 600 V capacitor. I'm using a power MOSFET for this application. I need it to ...
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35 views

Choosing Common Logic Level HF Buffer

I need help in choosing a common logic level buffer for a 555 timer output that will vary in frequency. I'd like to use n-channel/p-channel MOSFETs though I'm also open to cheap IC buffers. ...
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30 views

Current capabilities of P-Channel Mosfet Circuit

I don't know how to ask the right question it would appear, but the following answer by Dave Tweed Refers: Floating Voltage to Bias a P-Channel Mosfet without Exceeding Source-Gate Max Voltage In ...
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72 views

How to convert a 3.3V signal to 5V for a Mosfet gate

Based on the question 4-5-v-on-gate-of-mosfet-while-switch-open I ask this more generic question. Main project: I want to create a 16x8 (or so) multiplexed LED circuit Sub project: Creating a 2x2 LED ...
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43 views

This SR latch built with 180nm CMOS does not work in ltspice. How do I fix its behavior and parameters?

EDIT: I copied over the latch from another larger model that had Vdd defined, but missed it when copying over the design. However, after adding in Vdd, I still run into this confusing issue where the ...
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3answers
74 views

How to replace relay with N-Channel Mosfet

I have this simple circuit which uses a relay to charge and discharge a capacitor. Now instead of a mechanical switch, I want to use an electronic switch such as a N-Channel Mosfet. How can I ...
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50 views

Driving a motor backwards and forwards using mosfet and Arduino pin safety

So I want to drive a motor from a handheld drill/screwdriver. And I have managed to get it going using the first schematics, and using pwm to control the speed. The Zener diode is there to protect ...
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39 views

How does work the trigger/start of this buck converter?

Im watching this video but since its in german I dont fully understand the way it works, specially the startup side with the pulse source and the mosfet. Could someone explain me this part of the ...
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58 views

4.5 V on gate of Mosfet while switch open

I have a strange behavior with the circuit below. (the bidirectional logica level should be read as: VL = Voltage Low GNDL = GND Low VH = Voltage High GNDH = GND High L1 = Low channel 1 (I did only ...
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32 views

AC MOSFET H-bridge

Would appreciate an explanation of how this circuit works. It is a MOSFET H-bridge that takes a square wave input and either passes it through unchanged or changes its phasing 180 degrees. The “...
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38 views

How to make a bidirectional power switch for negative supply rail controlled from logic level MCU

I'm looking to build a bidirectional power switch for a negative power rail. I have a +12V, +5V, +3V3 and -5V supply to switch. For the positive supplies, I'm using two P-channel mosfets in a common ...
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34 views

Controlling a PWM'ed DC fan from 24v instead of 12V source

I have a tiny 12V which consumes ~0.07A and i was wondering if i can PWM the 12V fan with a 24V source at a 50% duty cycle through a ardunio and a mosfet. Would that work or fry the fan as the voltage ...
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48 views

How do I exactly calculate the amount of heat generated in MOSFET?

I am using two IRFP260N MOSFETs (datasheet) in parallel for my application. I am using it to drive a motor rated at 24VDC and consumes 8 to 10 Amps. I found some answers here and calculated the ...
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2answers
80 views

How can implement a low pass filter with this PWM signal? (Deadstop Fan won't start error)

I want to low pass the signal to the fans in this circuit. PWM frequency is 35khz and I calculated that I would need C = 10 µF and R = 10 Ω But no matter how I place my capacitor and resistor, ...
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41 views

Mosfet equivalent

I'm a newbie and been reading so much my head is spinning. Could someone please tell me if I can use irf530 mosfet to replace irfz44n mosfet in a car audio amplifier and please point out why or why ...
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28 views

Why are the pins of an UDN2981 related?

This question is related to this question: udn2981-maximum-output-current-too-less. In the UDN2981 datasheet, the picture below shows the maximum current (page 14, bottom left picture). Since if I ...
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117 views

Raspberry Pi not Compatible with Mosfet?

This is my mosfet datasheet RFP30N06LE i have my schematic setup exactly like this (except powering a 12v load not 60v) and even confirming with a multimeter when i set my gpio pin to high that there ...
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121 views

Large negative current spike in N-Channel MOSFET source when turn-off

I am working on repairing a power supply board of a LCD TV (200W power), more specifically, the PFC section (active power factor correction). See schematic (adapted from here): I've replaced some ...
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61 views

Converting 0-5V PWM to 0-10V PWM using Arduino and Mosfet not working

I am trying to convert 0-5V PWM coming from an Arduino to 0-10V PWM to run a motor which has PWM line that operate for 0-10V. But as soon as I connect the PWM line to mosfet it either shows only ...
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1answer
99 views

Driving IRF9530 MOSFET with 5V

I want to drive the IRF9530 P-Channel FET with 5V PIC microcontroller. My load is 3.2A. schemtic shows one row in my LED matrix. Scanning @ 1/16th rate, so peak current per LED will be 64mA and the ...
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76 views

First ever MOSFET use, is my schematic correctly using it?

I want to build a hybrid board that can either be powered by unregulated 9-15v power supply, OR, by a regulated one (that is to be also powered by a li-xx battery and also to charge it using a ...
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1answer
82 views

amplifier for 10V LED dimmer control using Raspberry Pi

My problem is I need to have an amplifier circuit design - schematic + components BOM with specific model information that is able to provide a dimmable output signal (Vout) 0.2-10V <0.8A for a set ...
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55 views

Trying to have NMOSs in parallel while passing current through only one at a time

If I wanted to have a bias current I1 going through M1 or M2 and I want M1 to alternate between on off (M1 on/M2 off, M1 off/M2 on) would this work? I simulated this with spice and for the first ...
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46 views

H-bridge design for Peltier

I am using a pelter module to cool a chamber, I also use the same module to heat the chamber just by reversing the voltage to to.(separately tested and working). This lead me to look for a H-bridge IC ...