# 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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### switching frequency 5206-2G

I would like to use the 5206-2G H-bridge for my wireless power transfer circuit, but i can't find the switching frequency which the FET's can tolerate. I have looked several times at the datasheet, ...
31 views

### Advice for P-Channel Mosfet in Depletion Mode

i want to be able turn off a led with a mosfet and a pushbutton. In order to do this i want the led to be in off state when voltage is applied to the gate of the mosfet. After researching for a while ...
668 views

### What is the difference between CPU transistors and generic ones?

Recently I had to build a h-bridge driver for my project, wireless power transmission. I learnt that I needed to have dead-time in my PWM signal given to IR2110, which doesn't have any dead-time ...
38 views

### How to ensure no quiescent current through signal source in a common source amplifier

Generally,coupling capacitors are used to block the quiescent current in an amplifier from flowing into the source and load. But one of my homework questions required me to ensure that the quiescent ...
39 views

### Old monitor’s internal power supply works only when heated from the outside…fixable?

I have this old LG Flatron w1934s that worked fine until it‘s power indicator led started flashing, and after a long while the monitor turned then on, if I heated the monitor’s back with something ...
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### 5VDC Fan Circuit

I have a 5VDC fan (AUB0505HD), and my ultimate goal is to drive this fan using a 3.3V PWM signal from a Raspberry Pi Zero. I haven't worked with transistors much outside of EE school, so I don't ...
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### High voltage Mosfet driver stage

In the schematic above I designed a high voltage Mosfet driver stage with some bipolar transistors. The simulation worked so far so I decided to build the circuit. Frequency response is pretty bad ...
16 views

### Diode and MOSFET SMT replacement

I am working on an Arduino project where am controlling a motor through one of the Arduino I/O pins. The motor has nothing special just a regular 3-5V motor. In my circuit am using a diode and a N-...
42 views

### Gate-Souce resistors needed?

I completed an IR emitter circuit with two selectable power settings. It's working on the breadboard and I'm asking if I need the gate-source resistors for stability? As the circuit is battery powered ...
72 views

### MOSFET small signal model output resistance

I am wondering what is the output resistance of the circuit below. I found that it depends on the gate voltage: \begin{aligned} R_{out} &= \frac{V_{out}}{I_{out}} \end{aligned}  \begin{...
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### Alternative for THT component with SMT

Am working on an arduino project where am controlling a motor through a I/O pin turning it ON and OFF, circuit below: Now am trying to make a PCB out of this circuit, to do so i wanted to switch ...
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### Opamp Burn up in constant current circuit

I designed a programmable constant current power supply to control two solenoids(electromagnetic).For the solenoid to open and close proportionally(it can move between fully open to fully closed and ...
42 views

### Simple CMOS switch with weird voltage in LTSpice

I am new to all this, so please forgive me, as I feel the answer to this must be so simple. I tried to build a basic CMOS switch. It has a supply of 5 V. There are periodic pulses of 5 V supplied to ...
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### Single Input Transconductors Implementations in IC

In my lecture notes I have these following configurations for realizing single input transconductors in integrated circuits: I have the following questions: Consider the first circuit: the drain ...
3k views

### MOSFET source measures 12V, still nothing will turn on

Please, bear with me, I'm a real rookie at electrical engineering. So please be easy on me. ;-) I've got the following circuit. I have a 5 seconds HIGH / LOW interval on ...
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### SIZING steps and Interpreting Mosfet datasheet

After reading those Interpreting Maximum Power of a MOSFET from the datasheet How to interpret Vgs(th) min/max in a MOSFET datasheet? https://www.infineon.com/dgdl/Infineon-...
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### P-Channel Mosfet switch and Capacitor Discharge on Drain

I'm using the following circuit with a P-channel mosfet to switch the positive line to a transceiver. I want to keep the transceiver grounded and switch it off to stop current draw from the battery. ...
61 views

### Change current in steps for pulsed LEDs

I want to control the power consumption and intensity of a IR LED which is fed by a 38kHz signal. Can I add mosfets in series with different resistors (25/250) like in my schematic? Application is a ...
26 views

### SD211 Replacement [closed]

I've just been informed that the SD211 is essentially obsolete. Would anyone have any recommendations for ultra-fast switching MOSFETs? I'll be using it to generate nanosecond pulses.
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### Logic level MOSFET gate trace length

I am using a micro-controller to switch a logic level MOSFET (the IRLR3103). The output of the MCU is 3.3V. I have a 1K resistor in series with the gate as well as a 100K pull down resistor as close ...
49 views

### Mosfet control Rds on , and Vgs

I want to know how to calculate Vgs , assuming load current Id is constant , Vd = voltage of battery is constant , and fet is operating in thermal stability region , so there is no thermal runnawy , ...
63 views

### Current spikes when MOSFET turns on and voltage spikes when MOSFET turns off

I studying for my Power Electronics course and have come across something which I can't seem to wrap my head around. In a lab, we built a buck converter with an inductive load and measured various ...
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### Reverse Polarity in rush Protection 2 p fet parallel

after reading those links : Reverse-polarity protection P-channel MOSFET Optimal method for multiple MOSFETs for LED driving with a shared power rail Parallel MOSFETs and this pdf : ...
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### Sizing of Inverter Circuit

I'm just embarking on a new design assignment and I was wondering - where do you guys start with sizing? What's your train of thought? So many devices, which do I start with first? The circuit is a ...
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### Diode Connected MOS

let's consider the equivalent circuit of a diode connected Mosfet. Since the current source between drain and source is: gm * Vgs = gm * Vds and it is proportional to Vds, it means that this ...
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### Power zener with mosfet + zener

I have two solar panels in series giving ~106 volts when open circuit and around 4 Amps when loaded. My mppt controller could accept 150v on the input, but it blew up when the battery was ...
75 views

### Bi-directional electronic switch for external circuitry

I am in the process of designing a PCB that is powered by a 10V / 1mA supply from a fandeck (incorporating EC/DC fan motors). One of the functionalities include having continuity between 2 pins on ...
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### Wireless RGB led controller circuit with motion sensing - design feedback

Beginner hobbyist here. I would appreciate some design feedback. Purpose of this circuit: It controls an RGB LED strip (5 Meters, SMD 5050) via an IR remote and also automatically powers on/off the ...
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### Current Sink with OP184

I got a question. I'm building a current sink for a project and below you can see what i came up with. I modified the Linear Tech. circuit (LT1492) because i wanted to have lower Vos. I also added 3 ...
31 views

### SIPMOS as current source

I read this question and I have the same issue: acquire and protect an input with 5-24V range. I wonder if nowadays I can use a BSS126 as current source transistor. It's a depletion mode N-channel, I ...
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### Why is an Enhancement P-Channel MOSFET Used?

I'm trying to design the power circuit for my project. I wanted to implement both USB and a LiPo battery to power it. I came across this circuit online but I'm struggling to understand how it works. ...
46 views

### Unwanted mosfet turn on and irregular duty cycle when driving with IR2110 how to fix?

I am designing an MPPT charge controller and testing all the different components. At the time of writing I am testing the buck converter. During testing, I used a 10 ohm load instead of the battery ...
86 views

### Increase Rise and Fall Time of this Schematic

The following cirucit converts a 3.3V PWM signal into a +-12V PWM signal and works as expected. I want to increase the rise and fall time of the ouput signal to approx 2us. How can this be done? ...
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### where can I get the h parameters for the BF998R MOSFET

Do MOSFETs have h parameters for modelling, If so where can I get them for the BF998R. If they do not exist are there other types for this device.
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### Working principle of a MOSFET Transistor

I was just reading a blog entry regarding the power conflict of the Arduino and trying to understand everything, when I came to a point where I could not understand the working principle of the ...
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### nmos reverse current protection

Let's assume I have a voltage sources V-A (like Arduino) and V-C (like Computer) and there is a load R-B (like some bidirectional thing) in between. I want to power up the R-B from either voltage ...
61 views

### Op-amp based over-current protection circuit not operating as expected

I am trying to make an over-current protection circuit using an LM358 opamp and an N-type Mosfet. I have only done it on Proteus simulation, not in real life. The problem I am having is that the ...
39 views

### 9V 1A adapter and 2*3.7V battery IRF9630 produce sound and gets very hot 9V battery not (metal detector)?

I am not an expert at electronics.I am trying to build a pulse induction metal detector. I have this circuit from that Book I am using it with stm 32 blue pill but I have to stabilize the 9v supply ...
22 views

### MOSFET Common-drain amplifier configurations

In my text-book is shown this circuit for Common-Drain Doing practice, I found this exercise What does it change between these two configurations? Voltage gain, input and output resistances, lower ...
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### What is wrong with the MOSFET IRF540N ? Even with the zero gate voltage, why current is still flowing through drain to source?

Actually I was developing the overcurrent protection using op amp LM-358 as described in the second picture . I made the circuit as described on this link https://circuitdigest.com/electronic-circuits/...
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### Strange MOSFET Common-Source with RD=0

I was trying to solve this circuit(find the Q Point, voltage gain, input and output resistances in midband region, the lower cutoff frequency using SCTC method), but I was confused by the absence of ...
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### N-channel MOSFET in low-side switch allows current to pass when off

I am attempting to replicate the circuit below on a through-hole breadboard and am not getting the expected results. The "Bed-Heat" input on the far right of the schematic is a digital signal from a ...
58 views

### 10kV high voltage switch using mosfet stack

I need to make a pulse generator for a 10kV power supply, few mA. Surprisingly, I could not find any standard design of HV switch using mosfet (Sic or not) stacks. Could someone give me some ...
63 views

### Charging a Li-ion battery with a Buck Convertor & ATmega8 [closed]

I'm trying to charge a 7.4 V Li-Ion battery following the CC/CV protocol and have a few questions. I want to use an SMPS from my old laptop that can provide 20 V/3.25 A and feed that to a buck ...
31 views

### MOS working point in a differential analog mixer

let's consider this simple configuration of a balanced differential mixer (analog multiplier): I have understood that the local oscillator is generally a high signal, while the radio-frequency signal ...
47 views

### USB cut off with N-MOSFET

I would like to use a N type mosfet in order to cut the current from a USB charger. The mosfet reference that I currently have is an IRLB8721. I have already done a similary thing to another project ...
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### MOSFET Fails After Few Uses

I am attempting to use a N-Channel Logic Level MOSFET as a switch for a phone charger that runs on a 42V battery. I have a resistor circuit with an LDR that currently outputs 3.3v when LIT with a ...
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### Maximum safe gate current for IRFZ44N MOSFET

I'm designing a spot welder using a high-current car starter battery, and a handful of N-channel mosfets of the given type (IRFZ44N, datasheet1, datasheet2). A microcontroller (through some drive ...
I need to find the small signal parameter $r_{D1}$. I understand I must draw the small signal equivalent first, but I do not know where to label this resistance, or what exactly it is equal to. Also ...