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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What kind of MOSFET this is?

What kind of a MOSFET is this / how can I tell what kind of a MOSFET this is? The markings say C3L01 8D, and searching reveals that it's made by Toshiba, but I cannot find a datasheet, and it isn't ...
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74 views

MOSFET Drain - Source overvoltage protection

I am developing project of MOSFET switch that is going to be used as power switch device in application with 12S li ion battery. To keep power wastes in the minimum level, I have to provide the lowest ...
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Is MOSFET Drain Source resistance always affected by Drain Source Current? Is there an IC which is not?

Im trying to measure the voltage of a variable resistor in a voltage divider setup, where the current for the voltage divider is sourced and sunk through a pair of MOSFETS. I assumed that Rdson (drain ...
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18 views

important aspects about MOSFET in making PWM inverter

In making a three-phase PWM inverter connected to the same single-phase DBR and AC source, switching devices with real MOSFETs are going to be used. What are important aspects that I need to consider ...
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43 views

Generally, how do you describe the functions of the basic parts in a buck or boost converter? The parts are enumerated in the post [closed]

Here is a homework question I am answering. 1. Explain the function of the following parts in the DC-to-DC converter. a. MOSFET b. Schottky Diode c. Inductor d. Capacitor Here is an accurate basic ...
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Why specifically use a MOSFET and Schottky diode on a buck or boost converter and not other transistors or diodes?

My electronics professor is currently teaching DC-to-DC converters. He decided to drop us some theoretical homework and just postpone the experiment. He gave us some questions. This is one of those ...
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Need guidance for latching output of op amp (N-channel mosfet)

There are a lot of schematics online for high side switch latching using a p-channel mosfet or PNP transistor, (I) couldn't find any for low-side so I tried to design my own: simulate this circuit &...
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Facing problem in converting single phase arduino code into three phase for 5 level inverter

I am making 3 phase inverter using 5 level inverter technology using arduino nano. The code i am having is for only single phase 5 level inverter but i want to make 3 phase inverter using this code ...
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35 views

Junction temperature calculation

I have a question regarding the calculation of the junction temperature of MOSFETs and IGBTs. An estimation is possible with: $$T_j = P \times R_{th} + T_a$$ Let us assume that the thermal resistance (...
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64 views

How to use a N-Channel MOSFET for high side switching?

According to my research, mostly N-Channel is used for low side switching and P-Channel is used for high side switching. But if I want to use N-Channel for high side switching, what are the ways and ...
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31 views

Differential pair linear range

If I increase the tail current, will the linear range of differential pair (range of Vid when both transistors are on) become larger or smaller? According to this formula, linear range will increase ...
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Is there any purpose to source degeneration in a Common Source amplifier with acurrent mirror biasing

Say you have a cute Common Source amplifier and you have biased it through an NMOS Current Mirror connected to the source. The current mirror sets \$I_D\$ to a fixed value and consequently, \$V_{GS}\$...
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58 views

Efficient voltage auto-selection using MOSFETs - does it make sense to make an auto-select between battery power and external power?

I want to design a voltage-auto selector for a battery powered board that I am designing. First Question Now I could just connect the LDO of my board to the battery output of the battery charger IC, ...
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62 views

MOSFET switch not turning off load

I am using a n-channel MOSFET (AO3400A) as a power switch. Circuit is below. The issue I'm facing is when the EN pin is 0V, the LEDs are still dimly lit. The voltage across the load measures about 2....
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27 views

MOSFET - Body Diode protection

I want to build the cricuit like on the image below: V1 - Is a 14S LiPo battery(there would be fuse in real life between positive battery terminal and "BATTERY+" M1 - PMOS acting as a load ...
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39 views

Small signal gain

I'm struggling to find the small signal gain of the circuit shown below. I am trying to find the gain from Vout to Va. Note that Vout corresponds to the output of an amplifier. Any help is much ...
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38 views

Gate Driver Circuit Gives Unexpected Results!

I have designed around the LM5106MM/NOPB gate driver. Used two IPB017N10N5ATMA1 N-CHANNEL MOSFETS. This circuit has actually been used in another design in production by a engineering group beyond my ...
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39 views

Id, Vds calculation

Simple and strange, looking at datasheet of BSS138 (Graphs) for this circuit below which is always ON Saturation mode Mosfet, Rds-ON = 3.5 Ω, VDS-ON = 0.1 V to 0.2 V. Id should be 16.66 mA but ...
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33 views

Isolated gate driver for the Class D amplifer

I am trying to simulate the gate driver part for driving the MOSFETs in the class D amplifier with 4N25 optocoupler, not too sure if the connection between 4N25 and MOSFETs is correct.
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How can i switch 9VDC / 3VDC

I’m trying to make power selection circuit with 9V and 3V. When I open 9V, it’s leaking to 3V side. I’m using fets and bjts. How can I make this circuit clear?
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284 views

Are external diodes needed to protect these MOSFETs from back emf?

(note: this post has been updated as suggested by members) The schematic below shows a single coil to be pulsed by n & p FETs. Each FET has 100V ds breakdown and < 10 mOhm Rds. Vgs threshold is ...
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910 views

Using a diode-connected MOSFETs as a voltage divider

I have read that it is possible to use a diode-connected MOSFET as a small-signal resistor with a resistance of 1/gm (ignoring channel length modulation.) Also, the equation for gm is as follows: ...
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111 views

Discharging a capacitor through a depletion MOSFET

I´m building a device to remotely operate a solenoid through a data link. That device, which is powered by a 9V battery, has a step-up circuit to raise the battery voltage to +- 160V which, in turn, ...
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59 views

Linear regulator power consumption

I have this circuit linear regulator with UVLO so I would like to calculate the power consumption of this block any person can help me, please Vout = 1.5 V (Iss = 15.2 μA, Vout = 1.5 V, switching = 32....
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84 views

Is there something wrong with the way this thing is connected? [closed]

I have this mosfet connected to motor, to control it (on / off). I use 5V arduino signal to do that, but motor doesn't spin. I connected the grounds, checked motor and transistor - they work. What ...
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604 views

MOSFET blowing when soft starting a motor

I have a small SMD MOSFET [AO3400A] powering a small 12VDC motor which draws 1Amp in normal running mode (higher on turn-on but I can't easily measure that). When turning on this motor, it trips the ...
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56 views

What components are inside a port expander, how does it work? (Are they tiny MOSFETs?)

Do port expanders use MOSFETS internally to switch the pins high/low? My project is using a Raspberry Pi and a MCP 23017 port expander to sink some current (to GND through the port expander) from a ...
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48 views

PSU reverse voltage protection [duplicate]

I bought a lab Psu device and I would like to use it to charge 1.2v batteries. However the manual says that it's not reverse voltage protected and it might get damaged. After some research I found out ...
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42 views

Can drain and source length be smaller than minimum channel length in CMOS technology?

I know the channel width can't be smaller, but what about drain and source? Say, in 0.18u technology, what would be a typical drain/source length?
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Why does a circuit model of N-MOSFET exhibit a finite resistance between source and gate?

In the T-equivalent circuit model of a MOSFET in small signal analysis the MOSFET shows an infinite resistance between its gate and source when looking from the gate while it shows very little ...
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Understanding battery voltage detection circuit

I am looking for some battery voltage monitoring circuit and came across this one (I don't have reference now, will add once I get it.) It uses complementary MOSFET pair DMC2400UV to enable the ...
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44 views

Schematic review: prioritized power ORing

I am in the process of designing a circuit which will allow me to safely OR two power supplies. Constraints: 5V up to 5A from Vin_hi_prio up to 2A from ...
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Am I understanding I_dss of this P-channel MOSFET correctly?

I have a device that operates with a 3V lithium cell, but can optionally accept a secondary power input which disconnects the battery. This schematic shows my implementation of this function: ...
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55 views

MOSFET drain current during turn ON time

In the below picture, once the Vgs is greater than Vth, the current Id starts to increase linearly. But at the same time, Vds is higher and hence the MOSFET is in saturation region. In saturation ...
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40 views

How to drive MOSFET with 2.7v?

Okay, I have mini coreless motor drone. I want to make a bigger drone by replacing the corless motor with 180 motor. For that, I need to control 4 MOSFETs to drive four 180 motors. Here comes my ...
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36 views

Mosfet transconductance in the saturation region

what happens to the transconductance of a MOSFET in the saturation region if the gate-source voltage is less than the threshold voltage? Will the transconductance be negative since the equation is ...
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65 views

MOSFET: Purpose of a Gate Resistor

I am trying to figure out the purpose of the gate resistor in this circuit: Pictured are the UCC28700 flyback controller and the STD3NK80Z-1 MOSFET. My understanding is that the resistor(s) serve two ...
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40 views

Calculating output impedance without measuring open-loop output voltage of a push-pull Class AB MOSFET Amplifier

So I am building and analyzing a Class AB / push-pull amplifier implemented with MOSFET as depicted in the following schematic: R2 is the load. The input is an AC signal with 3V amplitude and 1KHz ...
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48 views

MOSFET Gate Resistor Problem

I am driving a STD3NK80Z-1 MOSFET at a rate of approximately 105kHz using the UCC28700 by TI, and I want to make sure my gate drive circuit is correct. I am going to use the schematic below as a ...
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2X1 Mux using mosfet

I tried to make a mux for implementing a carry bypass adder(carry skip adder ).The image attached is the mux I tried in ltspice. But it is giving me from x no matter what S is(btw -S and -S are ...
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61 views

MOSFET won’t turn-off at low drain current

I am trying to design a MOSFET driver circuit for a bi-directional DC/DC converter. The load current is about 17A rms Max. Max input voltage will be about 54V DC. The image below is not the whole ...
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36 views

What will happen if a MOSFET switch circuit is run without the source?

I have a situation where I have to supply the power to the MOSFET gate drive circuit permanently even when the main switch for source battery is turned off. It is because of the fact that the drive ...
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50 views

Calculating the pulldown resistance for a given MOSFET's gate problem

According to this topic ,how to get this formula, I use RC circuit and can't get this formula This is my answer, and I don't know where is wrong
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42 views

body terminal of PMOS in transmission gate

Why is the body terminal of PMOS in the transmission gate connected to VDD instead of its source? Why do we deliberately introduce body effect here?
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Logic level mosfet wont drive solenoid

I am trying to find out why my current mosfet is not working by looking over the datasheet. Ultimately I am just trying to buy a mosfet that I know will work, but I want to understand the datasheets ...
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61 views

MOSFET GS resistor

This figure show the MOSFET with GS resistor to prevent the MOSFET turn on, but I don't know why it would turn on. Why MOSFET usually add the GS resistor about 4k~10k? How to choose the resistor ...
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226 views

Two BJT transistor vs driver for PWM MOSFET

In some books and articles they say that to protect the MOSFET from overheating when working in PWM mode two BJT transistors are used as in the image, others recommend the use of a driver for MOSFETs ...
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55 views

3.3V GPIO output of esp01 interfacing to CMOS logic gates operating at 12V

I want to check this circuit for proper interfacing, I am interfacing a 3.3V output to CMOS CD4071 with supply voltage of 12V. -First I used a low threshold voltage NMOS TN0106 as shown in the circuit....
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145 views

What is the reason to put two MOSFETs in a series connection?

background first: I am currently trying to repair my old Pioneer amplifier (A-405R). The error description behaviour is a sporadic infinite triggering of the relay (marked blue one in the schematics). ...
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35 views

BJT based mosfet driver, what resistor values to use?

I designed this MOSFET driver for a 24V motor with parts I have in my junkbox: The idea is basically Q2 and Q3 make a push-pull driver to drive the MOSFET gate to 0 or 24V. This allows the use of a ...

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