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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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1answer
138 views

“Temporary boost” supercap

I have a 12VDC load (up to 10A) that functions correctly down to 8VDC. Sometimes (frequency: many seconds max, many minutes typical) the power source has a very brief (few milliseconds) drop to 7V. ...
5
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0answers
318 views

Mazzilli flyback driver mosfets keep failing

I've been trying to build a high voltage generator consisting of a high-voltage transformer and a Cockroft-Walton multiplier. I have actually tried several different drivers to drive a high-voltage ...
4
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2answers
410 views

Managing reverse currents using MOSFETs

I'm planning to use a chip with two 5V output pins to provide power to two systems: a MCU (attiny85, operating voltage: ~2V - ~5V) and a USB device (input current: 3A). On top of that, I'll have an ...
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3k views

Dual active bridge converter

I'm having issues calculating the power losses associated with the operation of a bidirectional isolated Dual Active Bridge DC/DC converter. The converter is controlled using Phase Shift Modulation (...
3
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0answers
86 views

How to suppress noise in my circuit

I illustrated what my circuit do as you see. Switching frequency is 800 Hz. When I increase the load, a noise is heard from my circuit. Here is my drain oscillocope view in frequency domain. What can ...
3
votes
1answer
198 views

Is there any advantage to using multiple tracks in this PCB design?

I'm fairly new to PCB designing, but I'm loving experimenting with it. Currently, I'm trying to develop a simple PWM circuit using MOSFETs to control an RGBW strip, using an Arduino with an integrated ...
3
votes
2answers
54 views

MOSFET pinchoff reduce current

I understand that in an n channel MOSFET as Vgs increases, electrons are attracted towards the gate forming an n channel. These electrons are responsible for the conduction of the MOSFET. As Vds ...
3
votes
1answer
152 views

How do actively driven mosfets or transistors react to floating source?

Attempting to add some lights to a car's "intelligent" lighting system. Want to make sure I understand how my n-channel mosfets will react to losing their ground, while their gates are still connected....
3
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0answers
207 views

Gate of a transistor and mosfet damaged

In my schematic, I found that the base of transistor Q7 (2n2222) was damaged. I tried to replace it with a BS170 MOSFET, and the same thing happened where the gate was damaged. The microcontroller ...
3
votes
1answer
299 views

Parasitic Capacitor current of an inductor

I am doing a double pulse test on SiC MOSFETs from 100-800 V and current from 20-80 A. The schematic is shown in figure (the values are not correct though). In my first round of tests (Figure 2), I ...
3
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3answers
1k views

Audio soft mute using optically isolated MOSFET

I have an audio signal running through a device that switches it over using a mechanical relay, as a result of the DC offsets and the parasitic capacitance on the output (which also connects to a high ...
3
votes
1answer
1k views

Finding the Mid-Band Gain of a Transistor

I am studying for an exam working on the current problem: simulate this circuit – Schematic created using CircuitLab I have already found: $$Q-Point = (I_{DS},V_{DS}, V_{GS} = (.783mA, 1.32V, ...
3
votes
1answer
245 views

Why does the signal MOSFET keep failing in this circuit?

The following is the power control part of the circuit I use in my car to control the wing mirror folding motors, the idea is that the whole circuit can power itself off after its done its job to ...
2
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0answers
53 views

Pulse Transformer design problem: cant understand for sure whats the reason or irregular output waveform?

A ferrite core pulse transformer provided with 12V PWM signal (as primary winding input voltage) as shown in Fig-1, produces irregular output voltage across the secondary winding as shown in Fig-2. I ...
2
votes
0answers
66 views

SiC MOSFET SPICE model not behaving properly

I have been trying to simulate a fully controlled full bridge using SiC MOSFETs and so far haven't gettng at least expected results. So I tried to check what is happening using a single MOSFET and a ...
2
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0answers
37 views

MOSFET as a Switch with 26 V Circuit

I'm pretty green with electronics and I've encountered a situation I need some help on. Any help would be greatly appreciated. I've created a circuit wherein I am inserting a logic-level MOSFET (...
2
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0answers
43 views

Automatic power switching between two DC sources with a switch to charging in the second position

I am designing a circuit which will automatically switch to be powered by a single 18650 when the other voltage source is disconnected. It will use a DPDT switch, the second position of which will ...
2
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0answers
47 views

Buffer-cum-Level shifter using dual MOSFET

I am putting together a Buffer-cum-Level shifter using dual MOSFET to deal with PWM signal for display backlight control. This 3.3V PWM signal is driven by MSP430G2452 and would be reaching the ...
2
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0answers
78 views

Switching speed of MOSFET and BJT

I've read on the internet that MOSFET is faster switching device than bipolar transistor, however, i don't understand why. Considering the fact that transconductance of bjt is grater than ...
2
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0answers
97 views

Humming and voltage drop on p channel Mosfet

I am designing a high side switch using P-Mosfet to drive a heat element. The Mosfet is driven by PWM from MCU, which in the test is around 40Hz, 10% duty. Here is the schematic I am testing. I am ...
2
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1answer
37 views

Mosfet channel length modulation

Consider the nMOS for simplicity, even in saturation, Ids grows with Vds because the depletion region around the drain grows too ...
2
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0answers
57 views

Calculate the junction temperature of a MOSFET during pulse

Hi all I have a question regarding using a MOSFET for a constant current source. I have found this question with some answers but it wasn't clear to me yet. I want to create a constant current LED ...
2
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0answers
250 views

Large negative current spike in N-Channel MOSFET source when turn-off

I am working on repairing a power supply board of a LCD TV (200W power), more specifically, the PFC section (active power factor correction). See schematic (adapted from here): I've replaced some ...
2
votes
2answers
34 views

R_on for inverter gate

What \$R_{on}\$ do I use to calculate the delay for an inverter gate? In my class we came up with two definitions of \$R_{on}\$, one for saturation and one for triode. Is there a certain mode I ...
2
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0answers
51 views

Can I generate following voltage waveform with single PWM FET?

I am designing power supply which must output following voltages at a maximum of 1.5 A stepped down from a 24 V DC supply. 24 V 13-15 V 0-5 V Waveform for one of the inputs requires following ...
2
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0answers
65 views

Controlling IRL2703 with 3.3V (Reading MOSFET datasheets)

I have an application where I want to switch on/off a resistive load (24V/300mA) from a 3.3V MCU GPIO pin at a rate of 1 HZ or slower. I also have some IRL2703 MOSFETs, and I wonder if they would do ...
2
votes
1answer
342 views

Is it okay to connect 2 lithium ion battery in parallel to a charger that can maintenance 4.2V? (more detail in post)

So I'm planning to make a charger that can charge multiple lithium batteries in parallel with hope to use recycled one. I fully understand that they are dangerous when you do it incorrectly, so I just ...
2
votes
0answers
65 views

Questions about a remote relay control application with a MOSFET

I need to control eight solenoid-valves for water drainage outdoors, remotely and simultaneously. The valves are normally closed (NC) type which I guess, in that context, means they open and let the ...
2
votes
0answers
286 views

High Voltage Cascode with MOSFET LT Spice Simulation

I'm an electronics engineering student and want to develop a high voltage switch with normal Si N-MOSFETs. After some research, I discovered cascode switches for this application. Most of these ...
2
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0answers
144 views

Inverter Design - High Side MOSFET - Slow Switch Time

I've posted previously on a similar issue which can be found here Overview: My design is a 3 phase inverter with: MOSFETS are STF10N60DM2 Gate Driver is 6EDL04N06PT I'm using only a single high ...
2
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0answers
182 views

How does a cascode current mirror maintain equal Vds of the bottom transistors?

A basic current mirror is shown below: The load and reference current relationship is affected by channel length modulation: In order to cancel the effects of channel length modulation, vds1 and ...
2
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0answers
75 views

NMOS bidirectional variable resistor: How to increase body diode barrier potential?

I want to use an NMOS as a variable input resistor to an inverting amplifier. The source is connected to virtual ground and the drain is connected to the input. I need to accomodate both positive and ...
2
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0answers
61 views

How does a MOSFET conduct in saturation region?

It is a simple question but I could not find a straightforward answer. When a MOSFET enters saturation region, the channel length starts to decrease, and the channel width is the smallest near the ...
2
votes
1answer
278 views

Programmable Electronic Load Design

I am trying to design a programmable electronic load for testing the PWM outputs of PLC controllers. The outputs operate between 5-36 V and 10-2000 Hz frequency. The output is supposed to tested for ...
2
votes
0answers
131 views

Measuring battery voltage, capacitor on drain (nMOSFET switching load)

I've got a schematic to measure a battery voltage using a nMosfet (triggered by a GPIO high level). The voltage is measured at the Probe (see picture). Can you tell me the purpose of Capacitor C1 on ...
2
votes
0answers
313 views

Adding a ferrite bead to source of mosfet (smps)

We are designing a SMPS (ultra low noise) based on TI schematics http://www.ti.com/lit/df/tidrgc2/tidrgc2.pdf (5V, 15W quasi resonant) In order to reduce EMI (we have some ringing across Mosfet when ...
2
votes
0answers
191 views

Load Sharing/Isolation Circuit with ADP5063

I'm designing the battery power/charging circuit for the Reform DIY laptop which uses a (big) LiFePo4 cell. For the charger IC I've now settled on ADP5063 as it seems simple and can charge with 1.5A ...
2
votes
1answer
520 views

MOSFET Sizing in Wide-Swing Current Mirror Design Exercise

TL:DR How do I know how to size transistors? This is the same problem as this one. Now knowing that I can change L, I know that my W/L ratio to make Von = 200 mV is roughly 6.75. Also knowing that ...
2
votes
0answers
182 views

What MOSFET circuit replaces a diode in a 48V 40A escooter?

I want to use a 1kW generator and convert my eScooter to a hybrid. The scooter uses a 48V SLA battery bank of 4x22Ah SLA batteries in series. I used a transformer from a 1200W microwave oven and ...
2
votes
3answers
2k views

Controlling PWM noise on power supply

I've got a problem I haven't been able to sort out experimentally and am looking for help from someone who knows more than me. I'm making a handheld prop with audio and lighting effects. In the past ...
2
votes
1answer
279 views

Proof of type for Current mirror and Early effect (Mosfet transistors)

Can anyone explain me how I can prove this equation below (4.19).I know that \$V_{GS1}=V_{GS2}\$ and assuming that M1,M2 is in saturation then \$ID=0.5kn(vov)^2(1+\frac{V_{DS}}{V_{A}})\$
2
votes
1answer
667 views

High side RC ESC switch

I've been designing a test bench for RC propulsion systems and for that I thought it would be nice to be able to switch the power to the ESC on/off. For this I designed a simple circuit which I ...
2
votes
2answers
802 views

MOSFET Amplifier: Maximum Signal Swing without Clipping

I have a degenerated common source amplifier. I want to know what's the maximum input signal I can apply before the output signal begins to clip. What I currently do is to increase the input signal ...
2
votes
2answers
279 views

P-MOSFET Dropper-Switch - Linear Region

I'm repairing an ECU board from a SCANIA generator. It works with 24Vdc, and on the last maintenance the technician powered it with 220Vac, so it blew up some components. I've managed to replace the ...
2
votes
1answer
143 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 ...
2
votes
2answers
480 views

Voltage drop @24V2A using a MOSFET with Arduino

I'm not really good with electronics but i'm really trying to learn as much as i can, so please have mercy on my question :) Hardware So, i have an Arduino Uno, a 24V 150W power supply, a 24V 48W LED ...
2
votes
0answers
380 views

Conduction angle in three-phase rectifier

In a standard three-phase bridge rectifier, which consists of 6 diodes, each diode (or thyristor) conducts 120º of the full 360º period. I have built a synchronous rectifier (for research purposes), ...
2
votes
1answer
194 views

Smart mosfets, logic level input(mosfet replacement)

Basically diesel heater ecu my car uses has an shorted "smart" mosfet BTS141, which drives the glow plug. I don't know much about it since i cant determine the manufacturer. Basically it accepts logic ...
2
votes
0answers
101 views

Input selection circuitry for USB/battery

I'm making a development board, and trying to sort out the input selection circuitry, where if a battery (3.7V lipo) and USB is connected at the same time, it doesn't damage the circuitry, by stopping ...
2
votes
0answers
171 views

Protection High side Mosfet driver with less solenoid connection

I suggest control solenoid. Solenoid will be connected externally via a connector. Steering is via high side MOSFET driver. The requirements are for detecting disconnection, short circuit and current ...