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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29 views

How should I implement a USB-C Power Mux Circuit with Enable?

I'm designing a device which can be powered by DC IN or USB-C. The USB-C is a DRP, so it may be tasked either with sinking or sourcing power. The DC IN may be between 5V and 20V, so from here I'll ...
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78 views

Heating up a nichrome wire, MOSFET got too hot

I'm trying to get a 37 AWG, 0.6mm diameter nichrome wire to reach 300*C so it can heat up inside of an enclosure and according to its datasheet that requires 5A, I cut out enough nichrome wire to ...
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124 views

Why does an LED remain glowing when MOSFET gate is open?

Hello, I'm working with an N-Channel MOSFET (Link to data sheet for the MOSFET - https://www.onsemi.com/pub/Collateral/FQU13N10L-D.pdf) for the first time on a DC motor project, and I'm trying to ...
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32 views

Stepper motor current consumption calculation

I have this Stepper Motor Driver and a Stepper Motor with the below Specs: Number of Phase - 2 Number of Poles - 10 Step Angle - 18deg Winding resistance - 10ohms Current / Phase - 600mA/Phase Rated ...
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52 views

Zero Gate-Voltage Drain Current (IDss) vs Drain Source Voltage (Vds) relation for PMOS

The Drain to Source leakage current Idss at Zero Gate voltage (Vgs= 0) is normally 1uA(max). However the relationship (or Graph) with Vds (Drain-source voltage) is not mentioned in Datasheet. Que: ...
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34 views

Running a solenoid pump with N-channel MOSFET

simulate this circuit – Schematic created using CircuitLab I'm trying to run a solenoid pump(L2 in the diagram) using a pulse generated by an Arduino. The pump is designed to run on rectified ...
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1answer
118 views

How can I reduce the high voltage input for 7805?

I need to take 20ma from output of 7805.My input voltage is Ac variable voltage (0-300Vrms).I am planning use to pre regulator for 7805 and full bridge rectifier.Maybe I can reduce input voltage of ...
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1answer
33 views

How to set the boost output voltage in this IC?

I want to use this boost IC to drive an LED string. I have 9 LEDs. 300mA forward current and 3V as typical Vf. Can someone guide me on how to set the output voltage of the LED string using that IC?
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4answers
58 views

Values between log scales in a graph

I have a LED voltage vs current graph. The forward current is represented in a log scale. Suppose my value is 120mA. Where should I place my point and what would be my forward voltage with respect to ...
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the non inverted input on TI UC3705 or UC3706 transistor dirvers not working but inverted works fine?

DATASHEET TI UC3705 I have a UC3705 running fine on inverted input digital signal on the pin number 7 at +5 volts and pin 6 at ground from my siglent SDG1032X with a square wave 5 volt hi and 0 volt ...
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37 views

Switch off device when battery is charging

I need to disconnect the rest of the circuit when battery is charging for safety reasons. I use a LiPo battery which it's charged with an IC that is powered by 5V DC thought a micro USB connector. ...
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137 views

Can a uC drive a MOSFET at 500Hz

I want to dim an LED strip. It's about 1.5m in total length and could work for prolonged time on a battery. If it weren't for the battery limitation I would probably just put a resistor in series, but ...
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72 views

What is the use of drain diodes in the circuit below?

This TC7920 driver will be driving a piezo electric load which may behave like a capacitive load at certain frequencies. There is another IC TC8220 which is the same except it is not having the drain ...
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How does this MOSFET/Op-Amp voltage regulator circuit actually work?

I am trying to understand the functioning of this circuit since I have read that it is appropriate for power regulation: Here is the explanation that I have found: The zener diode provides the ...
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77 views

How to select a gate driver for a 100% duty cycle MOSFET switch

I am designing circuit with a high-side N-channel MOSFET switch. The switch will be operated at 100% duty cycle. I decided to use a high-side gate driver since they have internal circuitry to boost ...
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2answers
46 views

how to choose diode for PWM of high amperage solenoid?

I'm making a pulseable solenoid circuit via PWM at around 20 hz. THe solenoid is a heavy industrial type that pulls a whopping 18 amps. My snubber circuit gets hot and burns up as the current is too ...
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38 views

Vds meaning in characteristic curve of a MOSFET

As I was wrapping up my design (which didn't include MOSFETs as switches tho, yet), I've realized I wanted to make it crystal clear for myself if I understand the thing correctly. Feels weird, but ...
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41 views

Buck with input feedback?

I made a ZCS buck converter for the following specifications: 12 V to 5 V, 50W, 200 kHz switching frequency. But in reality, the source might not be 12 V always, and may have fluctuations. Is there ...
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1answer
53 views

Voltage Doubler PWM Circuit

I have the following circuit here, a high-side N-channel MOSFET driver, with gate voltages being generated via the circuit in the middle/NE555 section. I'm wondering, how does the voltage doubler ...
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2answers
63 views

How can I switch on 12V 500mA supply to a load when a signal is taken from 5V down to ground?

I have a commercial PCB. On it is an IC with a pin that is pulled down to ground by a normally open switch. I want to turn on supply to a load when the switch is closed. simulate this circuit – ...
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1answer
135 views

One MOSFET slowly activates itself, the other won't fully activate

I built the following circuit. +3.3V GPIOs and +5V driven by an RPi Zero. Common-anode RGB LED wired to three IRLB3034 MOSFETs. These have Vgs(th)-min/max of 1V/2.5V. The GPIOs are supposed to switch ...
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44 views

How to drive P mosfet gate to ground in half bridge synchronous DC buck/ boost converter

The diagram shows the totem pole driver circuit for the Hi Side P channel Mosfet driven from PIC pin PWM output. This is part of a buck boost circuit running at 250KHz. The biased totem pole ...
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37 views

Cascode MOSFET Vds

Hi, I am having some difficulty understanding the statement underlined. How does M2 see Vb-Vth2 across its drain source?
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81 views

Get some clarification about bias stabilisation with Emitter Degeneration

A textbook I use talks about the effects of adding \$R_{E}\$ in a common emitter amplifier. For stabilization of the circuit due to negative feedback As the Device gets hotter, more collector current ...
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92 views

ESP32 grilled with simple MOSFET switch for 12V water pump

I've soldered a small PCB around an ESP32 with following components: ESP32 Dev v4 Water pump with 12-24V and 4.5-6W rating Power supply with 12V and 1A rating Capacitive sensor with analog output ...
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38 views

Adding activity indicator LED to 3.3V serial line using enhancement mosfet

I want to make a PCB with a STM32 MCU on it. I will only have a 3.3V supply rail for this PCB. I will be using UART for some communication (AFAIK it is ACTIVE LOW) and I am planning to have activity ...
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517 views

How is a MOSFET amplifier useful?

I was wondering why would anyone use a MOSFET amplifier? Since a MOSFET amplifier is nonlinear, it produces significant amount of distortion. To minimize distortion, textbooks suggest using small ...
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61 views

What kind of MOSFET to use with this battery protection IC

I'm working on this hobby project and I am trying to create a PCB for it. I want to power the project with 2 18650 batteries. Because the product needs to be used by other people as well, I would like ...
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1answer
51 views

How to prevent Current Limiting Circuit failing short?

I am utilizing what I believe to be a fairly typical current limiting circuit at the input of a DC/DC converter. I am driving the converter from a battery so I can never exceed a certain current or I ...
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1answer
38 views

Automatic power switch between USB and LiPo battery

I was looking at the design of Adafruit M4 Feather board. The board can charge a battery via USB (and power the board). When USB is disconnected, the battery take over automatically. What I don't ...
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302 views

Why are the voltages the way they are in this transistor circuit?

This question is about what my book calls "transmission voltage" when an nmos is conncted to the power source, or a pmos is connected to ground. It has a hypothetical diagram ass shown: It ...
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57 views

MOSFET Switch Always On?

I am having a problem where my MOSFET instantly starts conducting when I connect a power supply. I have the gate signal from an Arduino Nano, which is tied low. I am nearly 100% sure I have the drain ...
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58 views

Limit inrush current after emergency stop relay

I have a power board with an emergency stop (using a mechanical relay). The input voltage is 24V and on the power board I have multiple DCDC converters, some before the emergency stop and some after. ...
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1answer
51 views

Will replacing MOSFET with a MOSFET with lower rds(on) reduce the thermal characteristics?

I want to replace a MOSFET in a legacy product. The MOSFET is a P-channel Power MOSFET that is used for PWM switching purposes (VGS @ -12V, PWM is 20% @ 200us). The FET is switching in to a 200uH, ...
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What are the effects of additional layers in Power MOSFET in terms of internal resistance and its trigger voltage?

As you can see in the attached image, due to the additional doping layers between the source and drain the MOSFET achieves a higher control of voltages and therefore can be used in power applications. ...
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65 views

Why must the p type be connected to the power source, and the n type be connected to ground? [closed]

When we have mosfet transistors, why must the p-type be connected to the power source, and the n -type be connected to ground? I don't see what will go wrong if we do it the other way. But a book I am ...
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201 views

MOSFET based bidirectionnal switch

The below circuit is an attempt at having 3 isolated bipolar switches able to handle +/-20A. Voltage is below 10V when "conducting/enabled" and below 200V when not. IA1212 is an isolated DC/...
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52 views

Multi-Stage Common-Source Amplifier - When is it no longer a small-signal?

I have a question about the actual definition of a small-signal signal. We use it all the times in amplifiers. But how small is a small-signal? When does it stop becoming a small-signal? Take for ...
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50 views

Why does a MOSFET's drain current decrease when increasing the transistor's width and length, however the overall W/L ratio stays the same?

I am doing a simple NMOS simulation where my W/L ratio was set to 20. I then increased the width and length of the MOSFET, however the overall W/L ratio was still 20. One thing I noticed was the drain ...
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Why am I getting this annoying problem in Multisim?

I'm using the "edit model" button under the "value" tab of various components in Multisim. Some of the components give me a nice tabulated view of the components characteristics ...
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5answers
501 views

Understanding MOSFET characteristics

I am trying to select an n-channel MOSFET to switch a 12 V power rail. The use case here is to switch on/off a couple of LEDs which are wired in series. The LEDs (datasheet) can draw a maximum of 700 ...
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77 views

How do the pins on a bjt relate to a mosfet's pins? [closed]

I'm new to electrical engineering, and I'm a little stuck. I've got this circuit that I want to make, but I don't have any bjt transistors, and I can't buy any right now. I was wondering how base, ...
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319 views

How to effectively control a Peltier device with MOSFETs? (general design and heat issue)

First, I'm still quite a novice in the electronics, so may miss some basic knowledge, but trying to learn anyway. That being said, here's my situation: Goal: Control of the direction of the heat ...
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73 views

Which voltage is lower, 0V or -1V for connecting a MOSFET's source terminal?

In an NMOS transistor the source should always be connected to the lowest voltage. Does this mean that if the source was originally grounded, but then the drain was connected to -1V that the source ...
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60 views

Why are contacts used to connect metal to active layers but not poly to active layers? [closed]

In the CMOS layouts that I've seen, metal layers always seem to connect to n+/p+ active regions by using a contact, but poly layers are just laid directly over them. Is there a reason we don't use a ...
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97 views

Switching a current source with a MOSFET [closed]

Probably is basic electronics, nonetheless every time there is an explanation of using a MOSFET as a switch (both NMOS or PMOS) it is always with a DC source. However, what if I want to drive a LED ...
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50 views

Producing negative to positive square wave pulse

Situation I need 2 kHz -10/40 V square wave duty <1 % pulse to drive 50 ohm load. I have a working 0-40 V solution: PWM by MCU driving a N-MOSFET low side switch off a 40 V DC rail. simulate this ...
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Large-Signal Analysis of Diode-Connected MOSFET

I know that diode connected devices act as resistors in small-signal domain. However, two diode connected devices can also be used to divide a large signal DC voltage based on the square-law equation. ...
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42 views

Can we use bootstrapping technique for resonant inverter?

I am developing a resonant converter and could not understand which technique is not be used for the H-Bridge inverter so the MOSFETs can switch properly. I am using IRF540n N-channel MOSFETs.
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1answer
50 views

Circuit operation

I have the below input protection and filter circuit. I want to understand how it works. Can someone tell me the purpose of R0101 and D0102 and D0104? As far as my understanding level, when the ...

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