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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Minimum voltage supply for a MOSFET-based ring oscillator

I am trying to build a ring oscillator based on N-channel MOSFET like below: How to compute the minimum \$V_{DD}\$ required for the circuit to oscillate? Is this the gate threshold voltage (\$V_{GS(...
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50 views

IRLZ44NS mosfet + 3.3v gate

I'm considering using some IRLZ44NS mosfets that I have with an ESP32 that runs at 3.3v. Looking at the datasheet it says: VGS(th) - Gate Threshold Voltage - min: 1.0v, max: 2.0v It seems like this ...
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49 views

Why turn-on speed of a MOSFET is linked to diode reverse recovery time

Here is a quote from section 3.4 "Speed-Enhancement Circuits" in "Fundamentals of MOSFET and IGBT Gate Drive Circuits" written by Texas Instruments: When speed enhancement circuits are mentioned, ...
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Switching MOSFET with isolated gate

I am trying to isolate the battery which powers the gate control circuitry from the battery which powers the hight-current load being switched by the MOSFET. Here is the basic circuit configuration: ...
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How do I avoid a high DC current flowing through mosfet in my SRSSTC tesla coil?

There are 6.48 amps flowing through the mosfet but only 12 mA through the capacitor, L2 would be my tesla coil primary. How can I reduce the amount of components in my circuit and improve its ...
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52 views

How to control a boost converter by using pwm from Arduino [closed]

I am creating a simple boost converter that step up voltage in the range 5V-30V. The switch is a MOSFET controlled by PWM output of an Arduino (with additional necessary components.) I want to ...
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29 views

Current Mirror - Supply Dependence

I have a question about one of the current mirrors introduced in the "Bandgap References" chapter of Razavi's Design of Analog ICs. He has this: My confusion is about Equation 12.1. I know that ...
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71 views

Charge Pump-Based Gate drive supply

I have heard many people talk about using a charge pump circuit instead of a bootstrap approach when supplying MOSFET gate drivers with a biasing level for the high side. I have yet to see anyone show ...
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56 views

Using a depletion mode mosfet as a current limiting device

I have recently discovered the exciting world of depletion mode mosfets. Curiously, even in this document, I found nowhere that a depletion mode mosfet could be used as a current limiting/inrush ...
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47 views

LTSPICE P-Channel MOSFET

I'm learning LTSPICE and am very confused by the results coming from playing around with P-channel MOSFETs. I created a very complete test of P-channel and N-channel MOSFETs, and all the N-channel ...
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106 views

Driving MOSFET/IGBT - Why Miller Plateau is a plateau?

I'm currently trying to understand what the Miller plateau is: what the different parameters that influence the Miller plateau are, when it begins, and when it ends. I'm reading document "Fundamentals ...
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Equivalent to AO7400A MOSFET

My Dell laptop (Inspiron 15 7559) has a dead AO7400A MOSFET, and I've been looking all over for a replacement, but with no luck. Does anyone know an equivalent to it, or maybe somewhere I would be ...
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Simple Synchronous Rectification of Unidirectional Motor?

I'm trying to drive a high current, low voltage motor (24V 100A cont.). It previously used a very large and overpowered H-Bridge (16 FETs). The system only can rotate 1 direction, and is required to ...
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58 views

3d printer MOSFET can't use on car bulb, but can use on other load (ie. LED, dc motor, relay)

I want to use a MOSFET that can handle high current use for switching, so I decided to use the external MOSFET for 3d printer. I tested it out on other loads such as motor, LED, relay it is able to ...
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36 views

Why cascode is not used often as a power switch

Say, we are building a synchronous buck and we have some beefy 600V 10A MOSFET, but it is not really suited for high frequency application - we need to be aware of dv/dt limits and it is hard to ...
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55 views

Switched Capacitor with MOSFET

I have been trying to create a simple switched capacitor for my circuit, yet I must be doing something wrong and can't understand why it won't work. When the MOSFET is ON, VGS=3.2V, whereas when it ...
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29 views

Can an INA219 current sensor operate with a FET body diode present over the sensing pins?

I'm designing a board with optional current sensing modules (based on INA219) that can be plugged into it for monitoring the current on some 12V lines that go to peripheral devices. The schematic for ...
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60 views

What is the State of a MOSFET with a Constant Source Current and Floating Gate?

simulate this circuit – Schematic created using CircuitLab Suppose we have a NMOS transistor, with and ideal current source (I_S) in its source. The drain is connected to V_DD, and the gate is ...
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4answers
55 views

Reverse polarity protection on 5-12V input and output

Can someone help me with reverse polarity protection on 5-12V input and output using a using a P-Channel MOSFET? How can I calculate which MOSFET, resistor, zener diode I have to use? I use a 5V 10A ...
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51 views

Paralleling MOSFET Oscillation

I'm currently reading an application note about paralleling MOSFET and oscillation and it is written the following sentence : "In addition, parallel MOSFETs share a common low-impedance path, which ...
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1answer
51 views

Replace switching diode with MOSFET for lower voltage drop in charge pump?

I have seen reverse voltage protection circuits that use a pmos instead of a diode so that there is minimal power loss and voltage drop in that sector of the circuit. I want to make a charge pump for ...
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IR2110 MOSFET drivers burning

I am currently building an H-bridge for my Tesla coil with this video as reference: H bridge. The only thing I changed was that I swapped the pull-up to pull-down resistors and I am using IRFZ44N and ...
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Why is propagation delay a function of supply voltage?

In the context of FPGAs, it was brought to my attention today that propagation delay varies with supply voltage. When I asked why this was so, one of the FPGA designers stated that a logic gate is ...
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205 views

Heat Dissipation Calculation for MOSFET

My challenge at the moment is dissipating 60A of load current through an array of MOSFETs. Here are my specs: No cooling fans Heatsinks allowed, if needed FET and/or heatsink cannot attach to the ...
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59 views

Should I apply soldermask over SMT thermal pads?

On page 8 and 9 of the following datasheet, there's a description of thermal pads for this MOSFET: https://www.vishay.com/docs/63302/si2342ds.pdf What I am wondering is: I will design the footprint ...
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Using MOSFET to prevent Op Amp saturation

How N-channel Q1B MOSFET prevent Op-Amp U1B from saturation.Terminal 5 of U1B and Q1B are connected to output voltage of a DAC. At 4 of Q1B and Q2B is the same signal multiplexed to control LED.
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1EDN7512B MOSFET driver not working

I am facing some difficulty getting a 1EDN7512B driver from Infineon to trigger at all. The following is one of the simple test circuits I quickly threw on a breadboard to test, with no success. I am ...
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Driving laser modules with MCP23017 and MOSFETs

I would like to make a PCB to switch 16 laser modules on and off. The laser module in question is this one: https://www.sparkfun.com/products/9906 I believe the module already has a driver included (...
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21 views

High Impedance Load Driving with Mosfet as Common Source Configuration

I am just trying a design ac switch with mosfets which are connected as common source. Mosfets will drive 16.2A load in normal conditions. When I try to drive 10 ohm load with 162V (peak, 400hz), as ...
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Buck converter MOSFET (IRF4905) heating up

I tried to build a buck converter without any ICs, just transistors, a diode and passive components. Its purpose is to convert 12V to 5V at 2 Amps. It works, but the switching MOSFET (IRF4905) heats ...
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Do Protected Power MOSFETs need a flyback diodes?

There are protected MOSFETs under various marketing names available (e.g. omnifet, hitfet, intellifet, etc). These devices include clamping diodes and overcurrent/temperature protection. They also ...
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2 E-Mosfets connected in series calculations [closed]

So suppose we have two E-MOSFETS connected in series across a 10V supply, and the upper MOSFET has its drain connected to the gate, and the lower one is unbiased. (The input is taken to be the gate of ...
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31 views

Oscillations with paralleled MOSFET

I m actually reading a section of a book which talks about parralleling MOSFETs. The book talk about "Power supply design". There is a sub section which describes how to design the circuit layout. It ...
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56 views

Using multiple transistor to increase current handling

I need to make circuit that will convert 24v to 5v 4A. I have bought LM7805 mosfets and they are converting 0-40v to 5v 1.5A. Problem is that I need minimal of 4A at the end so connecting 4 ...
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63 views

Simple MOSFET circuit doesn't seem to be fully turning on

One of my current home projects is redoing the doorbell by retro-fitting a pushbutton and LED inside an older button housing which I already had and looks nice, but didn't come with a very good switch ...
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Inverted switch does not work consistently

I made an inverted switch circuit that turns off the LED when the switch SW1 is closed and turns on the LED when the switch SW1 is open. I made several circuits and some of them do not work as they ...
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161 views

P Channel MOSFET is not behaving with another MOSFET

This is a very simple (or so I thought) power switching circuit I made for an extremely low, power consumptive device. The device normally runs on a 3.6v lithium, but occasionally a user will plug it ...
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Controlling a 12V circuit with a RaspberryPi via PWM

I'm looking to power a 50W 12V heating element via the PWM pin of my Raspberrypi. For this, I have a MOSFET (STP9NB60) and a power supply. Of course this MOSFET's threshold voltage is at least 3V, ...
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Can someone explain this high-speed P-channel MOSFET drive circuitry?

I found this circuit in an application note on P-Channel Power MOSFETS. The note explains that modern technology has made it possible for P-Channel MOSFETS to approach N-Channel performance in power ...
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423 views

BJT 'Hard Saturation' Equivalent for MOSFET?

For a BJT, we usually want to hard saturate it by assuming Beta value is very low. This way we can maximize the current at the collector. However, I am not sure what is the equivalent for a MOSFET ...
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p mosfet calculations reverse polarity for high power ( 48 V , 30 A )

i want to make reverse polarity protection for input 48 voltage , load 30 Ampere 2 dc buck converters. i was searching many solutions like diodes , but i wanna make it with p fet , so i came across ...
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33 views

Charge Pump for P-Channel MOSFET

Many N-Channel MOSFET drivers for high side switches and high speeds have charge pumps that can provide enough current at high voltage to drive the gate high and sink the current back out again. I ...
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70 views

MOSFET Gate voltage

I have a series resonant circuit where I will have a lot of capacitors. I want to select a capacitor value for resonance for a particular frequency and want to turn on that capacitor using a MOSFET. ...
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89 views

Why cannot I edit MOSFETs in LTspice by “nmos”

update: I edited question so that it will be mainly related to LTspice OK, now I have used irfz44n for an example model, I realized that, by using the directive above(nmos), I am not able to modify ...
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Rs and Rd in series in MOSFET circuit?

Can we consider Rs and Rd to be in series? That is, is the equation ID = (Vdd)/(Rd+Rs) correct? What is confusing me is that they have the same current, but there's a voltage drop across the drain-...
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Mosfet data sheets [duplicate]

Where can I find the data on different components, like mosfet enhance n channel. If I use a mosfet enhance n channel transistor with a threshold voltage of 14V will it turn on at 14V if so what ...
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Switch that turns on and off as voltage changes

I want to control a 12 Vdc, 2 A fan. I'm connecting it to a battery bank in a sailboat. I want to turn on the fan when the voltage reaches 14 Vdc. When the charger turns off, the battery voltage will ...
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39 views

Turn off and turn in time of Mosfet

Why mosfet have different turn on and turn off time? If I am correct, mosfet have higher turn off time. Why?
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34 views

Turn-off voltage for SiC modules, does it always have to be negative?

I have been using SiC power modules for my application.Normally we use negative voltages at the gate to turn-off the modules. Would want to know if the power modules can be turned off with the zero ...
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69 views

65V Square wave Switching Circuit

I am trying to generate a 65V square wave very similar to the post found here: Mosfet PWM signal not square My load is in a slightly different configuration (i've tried them both ways), but the ...