Questions tagged [mosfet]

A 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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How to use a comparator to ensure that two MOSFETs do not conduct at the same time?

I have read that it is possible to use a comparator to ensure that two MOSFETs do not conduct in the same time, by allowing a MOSFET to conduct only when the other one does not. I'm unable to imagine ...
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Gate to Source Resistor turning MOSFET into BJT

Could I get a MOSFET to behave like a BJT (with respect to the large signal and hybrid-pi model) if I just tie a resistor from gate to source?
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Failures with MAX16127 chips

Recently I have started using the MAX16127 chip in my designs to protect against overvoltage conditions (Do-160G, Section 16.6.2.4 Category Z, for a very specific condition I am trying to survive, 80 ...
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MOSFET push-pull low current problem

I am trying to make a push-pull amp to drive a dc motor with a dual power supply. I have this circuit and it works but I can only get about 1A of current for each rail. Is it possible to raise this ...
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Why does this MOSFET not switch 9 V?

I am designing a circuit so that I can mute/unmute a microphone using an Arduino/Raspberry Pi. I am using a CD4051 which is designed for controlling audio applications. The schematic is based off of ...
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Need BSIM4 MOSFET model for 1.2 nm technology

I am performing a simulation of a 2-input NAND gate with LTspice software. There is only support for the 180 nm technology library. Can I use the 1.2 nm technology model? And if I can, where can I ...
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How is a bistable element formed with two inverters and two transistors in a 6T SRAM cell?

I'm trying to figure out how a charge can be stored between two CMOS inverters and two more transistors. I understand how the inverter works, just with a NMOS and PMOS base connected to a common ...
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Controlling MOSFET driver's input levels

I have a high-side MOSFET driver (MAX1614) that is used to power a device on and off. The /ON and /OFF pins of MAX1614 are connected to PCA9536 I2C-GPIO expander. The goal is to use a physical button ...
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Driving a lamp with low side MOSFET

I have a circuit based on 555s that flashes a 12 V 10 W lamp. I am using a MOSFET IRF540 to drive the said lamp. I have the output of the 555 (12 V) pulsing (on/off) once per second. The drain is ...
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Ultra-fast load switch

I have a question that I am assuming has a very easy answer (hopefully). I am trying to turn on and off the power to a pcb really fast, on the order of 1us. My problem is that my board has some bypass ...
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P-MOS control and capactive load

I am trying to drive an high capacitive load with a P-Mosfet. I added a PTC to limit the current, but it doesn't seen to be working. The mosfet is often killed. Can anybody help and provide a 'simple' ...
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Are small-signal MOSFETs without ESD-protection an actual thing?

I want to build a low-bias current (\$\ll\$1 pA) amplifier with a MOSFET for the fun of it. However, after testing the gate-source leakage current of some 2N7002s I was shocked that they leak roughly ...
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MOSFET keeps blowing out

I am trying to make a system that acts as a constant current/power load. At the time I am working with the power electronics, but I am having some trouble with the MOSFET in the circuit. Below is a ...
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Bandwidth: voltage-source vs. current-source gate drivers

Why do voltage-source gate drivers provide low-to-medium bandwidth that does not work well for wide band gap devices, while current-source gate drivers provide hundreds of MHz of bandwidth?
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What is the reason why thermal aging affects only the Cds capacitance but not the Cgs or Cgd capacitances?

Please take a look at the following images, experimentally obtained from a power cycling test of a power MOSFET. After the test where thermal aging is created due to repetitive power cycles, it is ...
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P-channel logic-level MOSFET that turns on properly when driven by an ESP32 (working from 3.0 V to 3.6 V) [closed]

I'm reading the specs of the ESP32 and I'm trying to find a P-channel MOSFET that I can drive with the GPIO pins. The specs say that ESP32 works from 3.0 to 3.6 V. Its logical zero is at most 0.1 VDD ...
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Help with circuit behavior

(All transistors are of the same size) (Both signal transitions occur at the same time) case 1: (initial stored value is 0) The PMOS transition didn't really matter, the X-coupled INVs were capable ...
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Final voltage at a node - calculation

Considering the following circuit: What would be the final voltage on Csn when its initial value is: 0+x (degraded 0) 1-x (degraded 1) I tried calculating this, and: I got a value of 0+x+2Vt ...
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What is the best way (using solid state) to power off lights when another light circuit powers on?

I am trying to build a circuit that will turn off LED license plate (LP) lights with the LED backup (BU) lights come on. The reasoning for this is that the LP lights wash out the reverse camera due to ...
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About MOSFET circuit behavior

When I look at the waveforms of simulated circuits, how do I know when their behavior (for example flipping value stored on a node, or an unexpected drop in strong level value...) is due to MOSFET ...
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Current-limited H-bridge

I attempted to design my own H-bridge (P-MOSFET high-side), using a comparator hooked to a one-shot to limit current, modeled after the one-shot current-limited schematic described here. Upon ...
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Why does a MOSFET gate respond to voltage and not current?

I am trying to make a variable resistor using a MOSFET, but the problem is that I don't want it to vary from voltage, but instead current. I understand that MOSFETs work by creating an electric field ...
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Why does MOSFET driver IC (FAN7392N) keep breaking when motor is connected?

I am creating an ESC for a BLDC motor. Here is my schematic: I'm still in the testing stage to make the motor spin with this ESC and while I'm testing, somehow the FAN7392N ICs always break and I ...
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Is the dot on an eight pin MOSFET the source or gate?

I watched a youtube video explaining that the dot indicates the start of the source pin segment, and the 4th pin on the same side, is the gate. With a DMM, I get continuity between the dot pin and ...
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MOSFET current limit for reverse battery protection

I am working on a board with a battery that sits around 3.7V. I was using a diode as a reverse polarity protection, but I wanted to switch it to a MOSFET so I'm implementing this circuit. I know ...
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Totally misunderstanding how a PMOS works? PMOS not turning off

I'm trying to use a PMOS to inverse an on/off signal. This is for a battery powered application. VSNS pin is connected to MCU GPIO. By design the rotary encoder channels A/B (detent type) are always ...
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Operation of charge pump gate driver

Can someone please help me understand how this circuit works? It's the block diagram from the MIC5014 high side gate driver. Some specific questions: When the input is off (low for the MIC5014, and ...
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MCU self power off switch

I want to create a auto power off circuit for a battery powered sensor to preserve the battery. The switch will be a reed type and the trigger pulse will be brief (~70 ms is my guess, shorter than ...
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RLC resonator to produce beautiful sine wave

simulate this circuit – Schematic created using CircuitLab I have read about the RLC tank which can help to resonate a pulse wave of a certain frequency so that it will produce a beautiful sine ...
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Power source switching circuit

I'm trying to design a circuit that will switch between two power sources using commands from a Raspberry Pi. Both power sources are 12 V and the desired output voltage is 12 V and max. 2 A. How I ...
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PWM MOSFET choice to power large DC motor and control inrush current

I have a 4 hp, 90 VDC, 12A @ 5200 RPM treadmill motor and a 80 V, 6 Ah lithium battery. The project is to use this motor to convert a lawn riding mower to electric using a tractor transmission and ...
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Is the Rds(on) of a MOSFET typically specified at the boundary of the saturation and triode regions?

Datasheets specify the Rds(on) of a MOSFET at some specific gate-source voltage, e.g. 100mΩ @ Vgs=4V. Up until now, I assumed that the test gate-source voltage was essentially arbitrary and chosen ...
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How to calculate accumulation charge concentration (/cm3) as a function of dist. from the oxide-semiconductor interface in a MOS cap with n-type semi?

I am trying to calculate the accumulation charge concentration (/cm3) for the MOS capacitor with Au/TiO2/n-InSb, where n doped InSb is the substrate. So far the material I found focuses on p-type ...
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High-voltage (48 V typ.) switching circuit

I am working on a design where the input (48 VDC) has to be supplied to I/O when a particular condition is met and the rest of the time it should be grounded. A relay is ideal for this, but the PCB ...
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Building my own direction controller for 3-Phase sensored BLDC motor

I am new to this domain so I have researched and found a prototype circuit. I am working on two motors: 60 V, 800 W sensor BLDC motor 36 V, 300 W sensor BLDC motor I am looking for the right type of ...
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MOSFET gate failure caused by unknown reason

I have the below circuit (link to simulation). It represents the low-voltage interlock and high-voltage precharge & discharge circuit for my Formula SAE team's EV car. While most other FSAE teams ...
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Why do I see a spike in this transient?

I'm trying to measure the V/I curve of a solar panel by recording a capacitor charge curve. Here is the circuit: The DC source and R4 simulate the solar panel (I know it's not an accurate model). An ...
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Why does the current and gm of this MOSFET not follow their correspondent formula

So M1 is a 32nm tech MOSFET where its parameters are taken from nanohub (Resource: Tools: Nano_CMOS) and then included in LTspice. The first image has a transistor named M1 with L= 36nm and W=72nm. ...
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FET voltage-controlled resistor schematics

I am trying to design and build a circuit that will accept a 1 to 5 VDC input and based on the voltage offer a 30 to 240 Ω resistance. I'd like the circuit to be linear. ie R = 30 + 210 x (Vin-1)/4 ...
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Active diode not allowing full voltage through

I'm working on a transformer active battery balancing circuit and have it working except, due to the diode voltage drop on the secondary, I need an alternative. Since the battery cell voltage is 4 V, ...
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Switching PNP transistor by using an opto-isolator

I have a problem with a circuit as shown below. I want to drive a pump with the Pump_enable signal but no metter how is this signal state - high or low, the Q3 and Q2 tranistors are always on and ...
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Op-amp output as gate voltage to MOSFET

As I understand it, the MOSFET here provides negative feedback to the closed-loop op-amp configuration. Hence, Vout2 = 1 V. Thus, the current through NMOS = Id = 1 mA. So Vout1 = 5 - (RD·Id). Then ...
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SOA and varying VDS

In a hot-swap application the FET spends some time in the linear region/Saturation region before it moves into the ohmic region. Here is a snippet of the turn on waveform seen for a FET: Yellow is ...
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MOSFET Vgs(max) and built-in Zener gate-source diodes

Some MOSFETs have a built-in ESD protection in the form of back-to-back Zener diodes between source and gate. An example can be seen here. DMG2302UK internal schematic This particular MOSFET has a Vgs(...
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Paralleling MOSFETs: Can I use a common gate resistor? [duplicate]

Can I use a single gate resistor for switching two MOSFETs? It will only switch on/off the device. It is working well with one FET, but I want to make the FET warm up less. I want the switcher to be ...
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Understanding which P FET to use for reverse polarity protection

I use a Schottky diode as reverse polarity protection on earlier versions but have decided to change to something more appropriate and energy efficient. The voltage input on the left is a 12-14.8 V ...
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Workings of single constant-current source with four MOSFET-switched LEDs

Background I have several hundred RGB+White LED lights which are controlled by a driver circuit which is no longer manufactured, and trying to plan some maintenance and possible replacement of the ...
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High-voltage power MOSFET self-protection at low Id currents

Let's say the IXTA02N250HV MOSFET regulates high voltage in a common-gate topology. The resistive load in the source is very light and allows an output current of just tens of μA. The MOSFET's ...
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MOSFET choice - PWM LED strip [closed]

I'm looking to PWM an LED strip with an ESP8266 (3.3 V PWM signal) with the following characteristics: Red channel: 12 V, 300 mA Green channel: 12 V, 250 mA Blue channel: 12 V, 250 mA As I ...
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Variation of MOSFETs with same W/L ratio

In MOSFET devices (let's say NMOS for this example), I know that the drain current has a formula: $$Id=\frac{\mu nC_{ox} }{2}\cdot \frac{W}{L}(V_{GS}-V_{th})^2(1+\lambda V_{DS})$$ For this circuit: I ...

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