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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11 views

Does this Schottky provide MOSFET transient protection?

I'm studying the schematic for an electronic load available as a kit from Jameco: http://www.jameco.com/Jameco/Products/ProdDS/2161107%20Schematic.pdf There is a Schottky diode shunting the ...
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13 views

Pull up resistor in NMOS logic value

For my senior high school project I decided to build a basic CPU from discrete components. I plan on using a 5V logic level and the current design calls for around 2000-3000 N-channel MOSFET ...
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1answer
50 views

Fail circuit with N MOSFET, what is wrong?

I have a circuit with two DC power lines coming from BATT A (1A) & BATT B (2A) (two outputs of a power bank). There is a sliding switch on the power line of BATT A. I would like to keep only one ...
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2answers
67 views

Charging a capacitor with MOSFETs

I have this circuit: simulate this circuit – Schematic created using CircuitLab The idea is that a high at Vcharge will charge the capacitor and then a high at Vdischarge will discharge ...
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2answers
79 views

is a uA current FET or BJT circuit design possible?

I'm working on a battery powered circuit that is triggering an interrupt on an ic with an internal pull-up. The resistor value and normally closed switch can not be changed. The quiescent current is ...
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18 views

hall effect sensor as a toggle swich for a 12v strip of LEDs

I'm trying to use a unipolar hall effect sensor as a power switch to turn off and on a 12V strip of LEDs, powered by a 12V 6.6Ah battery. I just tested the current draw of the LED strip with a ...
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1answer
81 views

Significance of \$V_{GS}-V_{th}\$ for MOSFETs

What is this factor's significance? Please, don't give any long mathematical explanation. Seeing the drain characteristics I can easily place all the regions. But where does this \$V_{GS}-V_{th}\$ ...
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30 views

capacitor bank controller arduino [on hold]

I am trying to use a Arduino to make a capacitor controller, I am using two MOSFETS, one with the collector connected to the output of the capacitor bank and the drain is the output. The other ...
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1answer
125 views

Use a diode or a MOSFET with a backup battery?

I'm running off-grid 12V domestic electricity, with solar panels and leisure batteries. The charge controller sits between the batteries and the load, and occasionally, briefly, cuts out the load ...
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1answer
87 views

Blown transistor on control board. Am I correct that it is probably an N-channel MOSFET? (and help identifying)

Please see the image below. I was attempting to hack my espresso machine (my hack was working, then I re-designed the circuit...). Something went wrong, and I believe I blew an SOT23 transistor (Q2 in ...
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2answers
75 views

AVR to drive 12V 1A motor

I have AVR that needs to drive 12V 1A motor. I always used NPN BJTs (2N2222), but reading the datasheet says the MAX is 1A (which means I cannot use it here). Instead, I willing to use MOSFET. I have ...
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40 views

MOSFET as Variable Capacitor

I know mosfet can be used as variable capacitor.I would like to use a MOS as a capacitor by varying the gate biasing voltage.But I am kind of blank about how to start with the circuit.Any Ideas?
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26 views

High frequency NMOS switch — works when inverting logic, but not otherwise

I'm working on a high-speed (75 kHz) switching application that outputs a 15 Vpk-pk square wave and its inverse. I'm using an NMOS IC (FQP30N06L) and function generator for now. I've connected the ...
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2answers
47 views

3.6V 38khz 25 IR Led in paralel

I'm working on a proximity detection project to drive up to 25 IR led on 38Khz with 3.6v mcu.I'm planing to make them parallel with 100 ohm resistor (limit their current to 20ma for each led).MCU pwm ...
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0answers
16 views

Routing LFPAK MOSFETs

I am routing a PCB with MOSFETs in LFPAK (aka SOT-669, Power SO8) packages for the 1st time. They look like D2PAK. The manufacturer, NXP, advises to draw identical polygons on top and bottom sides, ...
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1answer
75 views

MOSFET Power Switch

I'm making an external power supply but I want the device being powered to have a power switch on it that turns the external power on and off. What do you think about the following circuit? The ...
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1answer
52 views

Replace MOSFET with SMT equivalent [closed]

I want replace 27N3LH5 MOSFET in TO-220 package with SMT equivalent. Mosfet in output stage of LED driver, Power Supply +12VDC, current up to 2A per channel. Mosfets have heat-sinks, but I don't want ...
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0answers
42 views

Overriding Mechanical Switch with GPIO

I have a mechanical switch that sends a current (~5Vdc) into one of two wires. simulate this circuit – Schematic created using CircuitLab I would like to add circuitry which can override ...
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1answer
43 views

TVS unidirectional vs bidirectional in Hbridge

I have used this circuit (I found online last year) to drive big dc motors without much thinking but with great success. http://obrazki.elektroda.pl/4961105700_1437649469.jpg : - But yesterday I ...
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2answers
49 views

Why doesn't this mosfet saturate in a configuration and not the other one? [duplicate]

I am playing around with Mosfet specifically irf 540.According to the datasheet ,Vgs is about 10 volt.I added 2 resistors to 2 different circuits to see if there is a difference in the component's ...
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0answers
28 views

Switching between batteries while charging

Let's say I have a 4 A current source and two 12 V car batteries, connected in series (with a tap in the middle). What in your opinion is the simplest MOSFET switching circuit, that would allow me to ...
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1answer
446 views

Simple transistor circuit with unconnected gate pin acts strangely

My brother and I were playing around with some new transistors we ordered (2n7000 n-channel MOSFETs), trying to make a simple switching circuit: connect a switch, LED turns on; open the switch, LED ...
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1answer
39 views

How a P-Channel Mosfet works with a pull-up resistor

I have been desperately trying for days to troubleshoot this h-bridge I build so I'm trying to completely understand it first. What I don't understand is how R1 and ...
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3answers
70 views

How to reduce the voltage dropped in a mosfet used as a switch?

I'm trying to use a N-channel mosfet as a switch for controlling a LED, but the most of the voltage is dropped in the mosfet itself (drain-source) and the led are not turning ON. The voltage in the ...
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1answer
43 views

What is the circuit for the PMOS driver found in synchronous buck regulator ICs?

Some synchronous buck regulator ICs sport a NMOS lowside switch and a PMOS high side switch. I understand why these use a PMOS/NMOS pair instead of a NMOS/NMOS pair, but I can't seem to make sense of ...
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1answer
108 views

Difference between drain and source current

I was looking at this datasheet and I am a bit confused. How it is possible to allow for a different current for the source and the drain? The datasheet states more A for the drain than the source. ...
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38 views

Plot Vx as a function of time

I am stuck with this question. According to my analysis Vx = -3V when Vin = 0V. But I cannot interpret the voltage at the gate since there is a voltage of 0V due to Vin and +3V from the capacitor. ...
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51 views

Driving multiple MOSFETS (IRF610) from one output of Arduino

Here's my question: I have a Arduino (ATMEGA328P) project that requires me to switch on multiple MOSFETs (up to 10 MOSFETs) from a single Arduino output. I'm hoping I won't need a relay or transistor ...
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2answers
79 views

Modeling long wires in circuits

What's the proper way to model really long wires in circuits (18ga, ~1500 ft)? I'm aware that over long lengths start to accrue non-ignorable resistances. I'm wondering if they start to get other ...
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2answers
96 views

Connecting a switch and a MOSFET to an Arduino?

I have an LED strip that I am trying to turn on with a magnetic switch when a door opens. I want the LEDs to fade on when I open the door and fade off when I close it, which is where the Arduino comes ...
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4answers
135 views

How to heat up MOSFET within seconds?

I'm using low power MOSFETs (N channel-STP4NK60ZFP and P channel- IRF9530). The aim is to build a demo kit for students to study the thermal characteristics of MOSFET at variable frequencies and duty ...
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49 views

MOSFET Drain, Source and Bulk connected to a source

Background: I have a circuit for a FGMOS and they are describing the Fowler-Nordheim Tunneling (FNT) mechanism. The picture features two transistors: the main (FG)MOS and a secondary MOS to ...
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3answers
96 views

Why use Optcoupler + Mosfet?

I saw this project: http://diyhacking.com/arduino-lamp-dimmer/ which I'm interessted to(except that I will have to use some 24V, still enough to hurt the Raspberry Pi). There is several things that ...
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1answer
20 views

Using a SMPS converter IC as a controller

I'm building an LED driver using the LM3410. The internal switch supports a current of about 2A which should be adequate for my needs, but if I need more, can I use an external MOSFET to act as a ...
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1answer
40 views

LiPO reverse polarity protection with P-Fet & charger

I am trying to use a P-FET to protect my circuit against reverse polarity like such: Now i would like to add a LiPo charger to this circuit. Can i just add it after the P-FET (@+Vbatprotected)? ...
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45 views

Small signal models of MOS amplifiers

I understand that the equivalent circuits describe the behavior of amplifier for signals of low amplitude that allow us to assume that the circuit behaves linearly. My questions are: Why are all ...
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0answers
14 views

PMOS bulk voltage affect NMOS V_t

I am using a MOSFET in a IC (CD4007), only the NMOS in the IC. Then, I want to know the parameters, \$ k_n\$, \$W\$, \$L\$ and \$ V_t \$, for this, I using a method for characterize the NMOS. The ...
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1answer
69 views

Replace Transistor with Mosfet?

I am using a circuit to drive high voltage display tubes (170V DC, 3mA). Currently, the tubes get switched by an arduino. The output pin is hooked up to a MMBT42 transistor and a 10kOhm base ...
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2answers
76 views

5V 5A rail controlled by 3.3v microcontroller - dual switching or power mosfet?

I think this is a common situation so hopefully an answer helps more than just me. I have a 3.3v low power MCU which will be controlling a 5v 5A run of LEDs. When the LEDs are off the system will go ...
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2answers
123 views

Driving DC motor using a single MOSFET, why does the motor spin without applying a gate voltage?

The arduino drives the gate of the mosfet (irf540n) just fine (I've tested it with an led + 100 ohm resistor) and now I want to drive a small dc brushless motor. I've connected everything properly but ...
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1answer
88 views

MOSFET Always On despite of Pull-Down

I'm currently trying to get the hang of using a MOSFET as a switch. My schematic looks something like this (it's the first schematic I've ever drawn, so please don't be too hard on me). ...
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1answer
109 views

Make an opamp go rail-to-rail on a voltage higher than opamp supply

So I've chosen to work with an High Frequency Opamp that can only use 5V for power (I can't use any other Opamp). But I need the signals to go Rail-to-rail at say, 24V. So naturally I thought I'd just ...
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3answers
57 views

Single MOSFET Amplifiers

Why is it that when I see single MOSFET amplifiers or even complementary ones (one NMOS and PMOS), they would use what in single BJT amplifiers would be called "Common Emitter Amplifier". The output ...
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0answers
26 views

Expression of Output voltage in Triple tail cell

I was reading this article in one of the journals. In this a D-Latch has been proposed from a basic triple tail cell. Now when i was going through this i saw the implementation of AND gate with this ...
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3answers
167 views

Op-Amp + MOSFET = Constant Current Power Source (?)

I'm trying to make my first circuit from Horowitz and Hill- a constant current source that sits above the load, and can (hopefully) source 1A. I decided to use the components I had on hand- an ...
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1answer
43 views

Reverse current protection on power-switching MOS

It was suggested in "Select power supply voltage using MOSFETs" that a second MOSFET can be added in series to prevent reverse current flow. My question is, can I just reverse Drain and Source on the ...
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0answers
50 views

DC/DC Converter MOSFET switching

I am currently building a SEPIC converter. The signal arriving from the MOSFET driver to the MOSFET seems all good, however the Vds doesn't seem to follow the drivers signal and it makes the MOSFET ...
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1answer
49 views

MOSFET Switching without gate voltage / LED Strip

I have ordered logic-level MOSFETS of the type IRLZ34N (for the sake of working on a Raspberry Pi) but I have problems in Wiring it up. I have so far connected: +12 to the +12v lane of the switch ...
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1answer
89 views

Body Diode of a MOSFET

So for some MOSFETs, specially with Power MOSFETs, the body diode is a flyback diode that (as far as aI can tell) can be conveniently added to the MOSFET's bulk as there already PN junctions (correct ...
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3answers
581 views

Driving highly inductive loads destroys mosfet driver

Background I am attempting to generate some relatively high voltages (>200KV) using a system of ignition coils. This question deals with a single stage of this system which we are attempting to make ...