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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85 views

MOSFET Drive npn/pnp

I want to drive a MOSFET gate with about 10V. I use the following circuit as described in Fig. 4 http://tahmidmc.blogspot.com/2012/12/low-side-mosfet-drive-circuits-and_23.html Is this okay? How do I ...
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79 views

How to fix my simple MOSFET power switching circuit?

In my design the goal is to create a simple switch between power sources using a MOSFET. J2 is just a connector for the main power source which remains connected VDD is connected to a USB port VREG ...
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126 views

MOSFET as a switch failed after 200k cycles - root cause?

The following is a schematic for a solenoid that failed after ~200k cycles. I found that the MOSFET drain to source failed short. I am getting~ 26 ohms resistance. The way this circuit works is as ...
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33 views

The simplest way to keep n-channel mosfet saturated by positive feedback

Actully it will be one way switch for a lamp based on photo-resistor input: To keep the mosfet saturated in the moment it turns on I need positive feedback. How to get it in the simplest way? I can ...
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1answer
39 views

magnetic rotary encoder 0.3V output voltage

I have a 24V DC motor with a magnetic rotary encoder. The encoder has a 5V supply voltage. The datasheet states that it has an output voltage of 300-700mV. I have also measured it, and it gives around ...
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How to reduce noise causing by MOSFET driver?

I am trying to get +/- 12V and +/- 5V voltage in my board. I am getting lot of noise on the primary side itself as well it is carrying to the secondary side. I am driving the MOSFET with 100KHz PWM ...
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1answer
201 views

Noise in FET reverse-polarity protection for ADC

I have quite precise ADC circuit. I want to protect input supply voltage (not ADC input) from reverse-polarity using FET transistor as shown on the picture below. I wonder: is there any noise / worse ...
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1answer
62 views

Standalone current limiting circuit for Ultracap banks

I've been experimenting with ultracaps for a while now and I have a very specific problem: I use the ultracapacitors to compensate for line inductances and general power filtering. When I install a ...
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3answers
127 views

Switch supply for external circuit

I have two circuits and want to on/off the supply of other circuit supply with one. I don't want to use a relay because of the dimension. What can I use for this implementation such as a mosfet, ...
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2answers
82 views

a transistor vs two transistor as a switch

my question is about the usage of the transistor. why does when I use a transistor as a switch, the led dimming first and then off. but when I use two transistors it directly switches off. These are ...
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1answer
160 views

Determine an 8-SOIC MOSFET for boosting current capability

I am a complete electronics newbie. I recently designed a set of PCBs for LED tail lights. I have a sequence controller for them that can can control 28 channels at 260 mA. What I want to do is boost ...
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Creating DPDT Solid State Relay with FETs

I feel like this should be a very simple question but so far I have not found a solution. My goal is to make the following DPDT relay circuit using MOSFETs: The goal is to connect INX to OUTX or OUTY ...
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1answer
84 views

What does this MOSFET do in this voltage regulation circuit?

In the below schematic, V_USB is connected to the +5V of a USB jack, that the user can plug and unplug. There is also a backup LiPo Battery, whose positive terminal is represented by V_BATT. From my ...
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1answer
153 views

n-EMOSFET circuit analysis

This circuit is n-EMOSFET circuit, VTH=3V, K=1mA/V2, find VGS, ID and VD. Vo = 15-3300ID ID = (15 -Vo)/3300 VD = 3300ID Since IG=0, VGS=VDS=Vo ID = (15 -Vo)/3300 = 1mA/V2 (VGS- VTH)/2 ID = (15 -...
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What should I use to make this MOSFET drop the gate-voltage even faster?

I'm trying to create a delay circuit like this. When I snapp on the push button, then the current flows from +3.3V to GND and bypass the 220 Ohm resistor, which is my load. But the problem here is ...
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2answers
36 views

Depletion Region Capacitance in MOSFET

Hi, I would like to ask about the behavior of a MOSFET as a capacitor, particularly at the onset of inversion/weak inversion - see Fig 2.6(c) At this stage in Fig 2.6(c), there is positive charge at ...
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51 views

Can I use 1 optocoupler to drive 4 MOSFETs?

I've this circuit and works correctly, now I need to control 4 MOSFET instead of 2, is the second schematic correctly?
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Level-shifting with limited ways to change the board

I have this circuit: simulate this circuit – Schematic created using CircuitLab Where: U1 is an MCU powered at 3.3V OUT is a GPIO the dashed box represents an external hardware that I cannot ...
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43 views

Using a NMOS as High Side Switch for 48V battery

I am evaluating IR2125 and IRS20752LPBF and IR2184 high side gate drivers to drive a MOSFET that is to be used as a battery switch for a 48V battery, the continuous current from the battery is around ...
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MOSFET REPLACEMENT 60R580P

My Samsung 43 inches plasma display blown the main fuse, i am suspecting that two MOSFETs, what mosfet can i replace 60R580P with I see one is measuring continuity and feel replacing all is better, ...
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37 views

What's a good resource with lots of problems on MOSFET circuits? [closed]

I'm looking for a book/resource that focuses on MOSFET circuits like Common source/gate variations, Differential pair circuits, current mirrors etc. with TONS of problems and questions.
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buck small signal modelling

I have a synchronous buck converter and my inductor current looks like this:- To add voltage-mode closed loop control, I need to do the small signal modelling of the converter. I am a bit confused if ...
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42 views

High-Side N-Channel MOSFET Driving

Is this an acceptable way to drive a mosfet? In this case, I'm trying to turn on a high current load, but in case the load is changing it's resistance/impedance, or in the possibility it's ...
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1answer
46 views

Bidirectional voltage and current switch using mosfets

I'm following this tutorial (spanish) which tries to create a bidirectional power switch usng mosfets based on this publication by texas instruments The concept of the circuit looks simple enougth to ...
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5answers
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Hard temperatures rises for a MOSFET

I'm a mechanical engineer and a high school teacher that is about to start mechatronics and electronics. I've built this simple circuit that has the purpose to switching on and off a 12 V / 25 W lamp ...
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2answers
126 views

Suitable Half Bridge Driver to control capacitve load

I am looking for a method to reliably and quickly charge/discharge capacitors. Each capacitor should be individually charged/discharged. The charge/discharge rate should be in the microsecond range (...
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1answer
69 views

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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What material should I use to insulate my MOSFET from a heatsink?

I have a heat-sink and I want to put two FET's on it. I know I have to insulate it so the metal showing on it doesn't connect and create a path. Is there any good everyday material that would work? (...
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2answers
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Class D amplifier - Offset voltage

I am working on an amplifier based on 555 triangle generator, a comparator and the IRAUDAMP1 as a guideline. My problem is that i have high DC offset voltage at the output (-1.6V). What is the ...
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0answers
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Why charge injection happens

When a MOSFET switch is turned off and goes from sample mode to hold mode, the channel charge exits between the source and drain terminals. My confusion is, why can't some of the charge go back into ...
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331 views

MOSFET terminology seems to vary in every article i read!

For someone trying to learn about FET's, it seems there is no consistency in terminology (unless i am reading things wrong?) Trying to understand a FET as a switch (for power applications). It has ...
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1answer
92 views

Half-bridge gate driver fried, how can I make my design work?

I made a half-bridge following the recommended schematics from the IRS2184 datasheet. However when I powered it, it triggered over-current and got quite hot. Here is are schematic and routing. I ...
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2answers
380 views

How to measure output voltage of this Li-Ion battery circuit?

I've designed an AtTiny85 based Lithium-Ion battery protection/boost circuit that monitors the battery voltage and cuts the battery power to the external powered circuit when the battery dips below a ...
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2answers
561 views

Schematic review

I'm designing a control circuit to operate a watering system. I've got a main inlet valve, four outlet valves, and soil moisture sensors in the mix, driven from a 25.4 V CT transformer. I was ...
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1answer
31 views

How do I cutoff power to ultrasonic HC-SR06 when it is not been used, to save power

I want to read an ultrasonic sensor data every 10 minutes and expect that the module should be turned off in order to save power. How do I do this? I tried with a BC547 and PN2222 transistor but I end ...
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1answer
116 views

Finding node voltages in a MOSFET circuit

simulate this circuit – Schematic created using CircuitLab Considering Vdd=5v I want to calculate the node voltages at P,Q and R.
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How do I find the right MOSFET for my class E amplifier? [closed]

I'm trying to build a class E power amplifier for my Tesla coil right now. The operating frequency is 4MHz, Vcc is 50V and the output power should be around 100W. I've used Sokal's QEX article to ...
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32 views

Isolated discrete GaNFET driver implementation for flyback converter, 500kHz [closed]

I am about to embark on a project of making a discrete GaNFET driver. It should be isolated with a signal transformer. Do you have any suggestions for literature or designs? Below is my current ...
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1answer
74 views

Which of these is the correct wiring of an RGB light strip with n-channel MOSFET for Arduino

In these 2 examples, they connect the source to the gate with a 10K resistor, and both source and gate are connected to ground (edit clarification: gate connects to ground via 10K resistor - source ...
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If I drove pin DP8 high, would the MOSFET Q1 let current pass?

I have this circuit in my hand. If I drove pin DP8 high, would the MOSFET Q1 let current pass or would it not let it? I also have the same question for DP9. What would happen if I drove the pin DP9 ...
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86 views

How does a MOSFET work? (FQP30N06L)

I read everywhere that there needs to be a certain voltage at the gate so that current can flow between drain and source. But in my MOSFET (FQP30N06L) drain and source are connected and current ...
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1answer
58 views

How do use a MOSFET for automatic switching? [duplicate]

I'm trying to make an oscillator, but I can't wrap my head around the MOSFET. I have a very simple circuit (drawn in a cellphone paint app) where the circle with an arrow pointed at it is the MOSFET. ...
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1answer
127 views

Solid State Relay using photovoltaic MOSFET driver

I am in the process of creating a High power Mosfet based SSR. The idea is using a photovoltaic MOSFET driver such as VO1263 (SIlabs have similar IC but it uses CMOS coupling to create the isolated ...
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1answer
43 views

Pi Zero / GPIO Pins / +12V Power and Sharing Ground

I need a sanity check on my schematics before I pay for JLCPCB to make my PCB board. Goal: To have my Pi Zero fire a pyro charge in a model rocket. Setup: GPIO-20 Sends a signal to the MOSFET Gate, ...
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1answer
4k views

Load Sharing charging circuit for Lithium polymer

Charging lithium battery while at the same time trying to use circuit didn’t quite workout, with problems like the circuit not turning on and the battery never finish charging. The battery is 3.7V ...
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2answers
121 views

Current flow in trailing edge dimmer

I was trying to learn something about dimmers for light bulbs. After some reading, I found that most trailing edge dimmers contain some variant of this: Found for example in this diy-project or this ...
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1answer
62 views

Transistor switch with capacitive load

The goal I would like to know how to connect a transistor (MOSFET) to a capacitive load. I would like to rapidly charge and discharge a capacitor. How do I do it correctly? I basically want the ...
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1answer
82 views

Trying to understand MOSFET Turn on Procedure

I am trying to understand the mosfet turn on procedure. This is from the following application note by TI. https://www.ti.com/lit/ml/slua618a/slua618a.pdf?ts=1613979703351&ref_url=https%253A%252F%...
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Bode plot in Pspice

I want to get the bode plot of the controller part of my Buck converter. For this I looked online and saw a technique that mentioned to add an AC injection source from the voltage output to the top ...
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3answers
119 views

P-Channel MOSFET has a really high voltage drop

I just got a new P-Channel MOSFET FQP47P06. In the datasheet it says it has an RDSon of 26 milliohms, Vgs(th) of -4V, and a max current of 47A, but when I hooked it up in a simple test circuit like ...

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