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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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 (...
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Output capacitance of MOSFET

I have read in several application notes that there exists a region called the Miller plateau where the current into the Cgd is large such that almost no current enters Cgs holding the Gate voltage ...
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2answers
284 views

Low power tube headphone amplifier design

I have never worked or even listened to tubes/valves before, so its about time I did. I wanted a simple design to work with being my first tube project, and have found this from diyaudioprojects.com: ...
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355 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 ...
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Power stage for VCR (Voltage Controlled Resistor)

I'm building a VCR (Voltage Controlled Resistor) using the LM13700 component. You can read more details on that here: Floating voltage-controlled resistor with LM13700: How does it work? The problem ...
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1answer
259 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 ...
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86 views

Danfoss BD2.5 on 12V starting problem. Good signal on only one gate of both driving MOSFETs

The winding resistances are OK, not shorted to ground. One of 3 compressor coils is 3.6 ohms (should be 3.5). Driver coil resistances is 0.2 ohm instead of the normal 0.3. Compressor turns 1/2 turn or ...
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100 views

Eagle SPICE MOSFET Simulation Has the Wrong Operating Point

Having a lot of trouble getting an N-Channel MOSFET to work correctly in any spice program. Trying something really simple to get started and I can't seem to get the MOSFET to "turn-on". ...
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1answer
106 views

Rectifier for bike dynamo

I'm building a lighting system for a bike, powered by a dynamo (typically rated 6V, 3W max). The load will include LEDs and a bit of logic (such as N555/ATTiny85 for blinking, etc.). I also plan to ...
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68 views

How to determine Vds(on) and Vds(off) for switching loss calculation?

In the Infineon Application Note, two of the parameters they've used to calculate the switching loss of the MOSFET are Vds(on) and Vds(off). Is the Vds(off) the blocking voltage? Where do they obtain ...
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Using a single MOSFET as an RF switch

I'm assembling a receiver kit from QRP labs. It is an inexpensive kit designed to cover HF. This kit has a BS170 at the input which I assume is intended to disconnect the receiver when the transmitter ...
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2answers
1k views

Connecting battery packs in parallel and series, each with their own BMS

Recently I bought cheap a lot of CASIO DT-9723LI battery packs. Every pack consists of 2 Sony 6th-gen Li-ion 18650 cells and its own 2s BMS. Here the question arises: Can I connect this packs ...
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101 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 ...
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1answer
178 views

Need help with 2 Transistor Current Limiter Circuit in LTSpice

I am new to LTSpice. I have attached a picture of my circuit below: The goal of the circuit is to provide current to the R1 until It is too high. Then the BJT will activate, shutting the FET off. ...
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2answers
85 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 ...
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97 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 ...
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496 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 ...
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1answer
535 views

How to make battery controller with arduino?

I want to make simple UPS with means of arduino, to learn the processes from it, and be able to record and monitor at PC. For the start i want to implement buffered usage charge mode. Logic is simple -...
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257 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 ...
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281 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 ...
3
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1answer
364 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 ...
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1answer
193 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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How to use MOSFET in avalanche mode?

I'm thinking of a very simple circuit to generate high voltage pulses, like this: simulate this circuit – Schematic created using CircuitLab The MOSFET in this case will turn on until the ...
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1answer
82 views

Help identifying this MOSFET

Trying to figure out what this is, and suitable replacements. Markings are "1 Wt 77" Cannot seem to find anything. Edit: I removed and sized it today, looks like 2.04 mm square package, ...
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1answer
359 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 ...
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30 views

MOSFET diffusion to substrate capacitance

in order to eliminate body effect one way is to connect the substrate to source when the well is for a single device (PMOS with a well in a CMOS for example) , but i read that it increases the source ...
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1answer
77 views

Small signal analysis of dynamic microphone preamplifier circuit

I am trying to do a small signal analysis for a dynamic microphone preamplifier circuit. The original circuit is using BJT but I did not have much experiences with BJT, so I switched all BJT to MOSFET....
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37 views

LTspice MOSFET stops charging capacitor past Vt

I'm building a buck-boost converter that transfers C1's charge to C2. In the schematic shown below, C1's initial charge is 4V. When I use switches instead of MOSFETs in the circuit, everything works ...
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55 views

Reverse polarity protection with a MOSFET, am I doing it right?

I'm creating a simple LiPo charger and I would like to add a reverse polarity function to the module. The source voltage is 4.2V, the maximum current draw is 2A. Is this schematic correct? The MOSFET ...
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72 views

Li-ion charge / discharge circuit with ESP32 and MOSFET

Here is what I’d like to do: Wire a circuit that can either charge or discharge a single li-ion cell (3.0 to 4.2 V) or just do nothing at all. An ESP32 controls the circuit (max. 3.3 V). An INA219 ...
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1answer
72 views

How to choose MOSFETS by using the datasheets infos?

I know all the theory behind the MOSFETs, how to calculate the Id current based on (W/L) and (Vgs-Vth) and etc. But, now that I need to project a real solution, I feel like all of this is kinda ...
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65 views

Replace USB diode with something else to reduce voltage drop

So I've made this circuit with a MOSFET and an Op Amp to select a voltage input to my battery. I sort of based it off the voltage selector circuit on the Arduino Uno board, but inversed since that ...
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107 views

Fast switch rise time techniques

This question is continuation of this question: High Frequency Square Wave Generator I am trying to drive a 400V supply and 50ohm load with an RF MOSFET which has a rise time of 3-4 ns and fall time ...
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49 views

How to find the total output resistance for a mosfet cascadinging with a bjt?

I'm working on an problem in school. The original circuit was much bigger but I replaced the two current mirrors with DC current sources for simplicity. I know \$R_{in}\$ for the mosfet is infinite so ...
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54 views

Switching n-MOSFET as Solid-State Relay

I'm trying to design a simple solid state relay that can be in the off state when an AC Source is applied (schematic one) and then source up to 150mA to a small resistor when that AC Source is removed ...
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54 views

How to drive MOSFET switches in a cascaded hybrid modular multilevel converter using a half-bridge driver “IR2103S”

I am trying to drive the MOSFET switches in a cascaded hybrid modular multi-level converter as shown in Fig. 1. Fig. 2 is used here to simplify the circuit and to present the problem (let's focus on ...
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54 views

Switching between power sources with microcontroller

I need a way to switch a load(a high power LED) between two different power sources(50v and 100v) using a logic signal, quickly(<500us) and repeatably. I was going to use an n-channel high side ...
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54 views

Need help for pointing out, source follower circuit with current source, designing NMOS

I'm not sure did I solve this problem right. I made \$ r_{o2} \$ , which is resistance looking at Q2 drain. So I can get $$ g_{m,Q3} = 1.8m(A/V) $$ from $$A_v = \frac{r_{o2} || r_{o3}}{1/g_m + (r_{o2} ...
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91 views

Why is there a positive temperature coefficient in a MOSFET?

When the temperature in a MOSFET increases: resistance increases and mobility decreases thus avoiding thermal runaway compared to BJT. But what is the reason for increasing resistance and decreasing ...
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84 views

Trying to identify MOSFET - top markings DAX620 1411

My RC car ESC MOSFET is burnt. I'm trying to find a replacement for it, but I can't find the number or specs anywhere. The MOSFET has these numbers: DAX620 and below is 1411. Can someone help me ...
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70 views

Constant current source with MOSFETs

I have a question regarding this constant current source circuit: I have seen this circuit with two BJTs (like in the figure), but sometimes T2 is a MOSFET (I assume for lower Rdson resistance and ...
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3answers
649 views

Is it better to have a higher Vgs than Vds on a MOSFET (n-channel)?

I've been studying MOSFET switching applications recently, and have been playing with the Circuit Simulator Applet here. In my diagram below, I have Vds usually set to either 12 or 14, as I am trying ...
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288 views

MOSFET Gate driver - negative voltage with Zener circuit

I was reading about minimizing MOSFET switching loss when I came across an article by Texas Instrument on how to use negative voltage, instead of ground, to faster discharge MOSFET gate capacitance. ...
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1answer
718 views

Designing MOSFET bridge rectifiers for high voltages

I've been looking into MOSFET bridge rectifiers, also known as "zero IQ" rectifiers, as a replacement for traditional diode-based bridge rectifiers. Here's a simple example: The benefit, of course, ...
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124 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 ...
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38 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 (...
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0answers
128 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
141 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 ...
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0answers
371 views

MOSFET input and output capacitances

I need some explanations about the MOSFET parasitic capacitances. Precisely, what I studied is that there are those parasitic capacitances: But generally in digital electronics texts I see that they ...
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307 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 ...

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