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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17 views
Using a N-Mosfet to switch a common cathode ledstrip
I am trying to drive a RGB-ledstrip using the following circuit: http://learn.adafruit.com/rgb-led-strips/usage
As I am using a Common Cathode led-strip instead of a Common Anode one as used in the ...
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3answers
110 views
PWM Control with MOSFET switch
I plan on using a 555 timer for a PWM signal (variable with a potentiometer) and a gate driver to use a MOSFET as a switch. Essentially, I am trying to take a +300V rail and "step" it down using the ...
3
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1answer
141 views
Synchronous DC-DC converter and fast diodes
I'm a bit at a loss when trying to optimize a DC-DC converter (Half Bridge) and selecting my MOSFETs.
Up to 200V I get good results (MOSFET switching times are fast ~ 20ns and the anti-parallel diode ...
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3answers
66 views
Substitute a MOSFET in a motor controller
I'm trying to build a CoffeeBot from MAKE magazine, and I had a question about one of the components. The circuit is pretty simple; it uses an Arduino to control a gear motor via a MOSFET transistor. ...
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1answer
166 views
Short Channel Effects and FinFET?
I read that FinFET transistors were introduced to avoid the problems due to downscaling of MOSFET size, ie reduce the Short Channel Effects (SCEs) like DIBL, Hot Electron effects etc.
But how does ...
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1answer
55 views
Designing stable PMOS voltage regulator
As a follow-on to the question "Using forward voltage drop of diodes with linear regulator" I am looking into designing PMOS voltage regulators.
General Topology
A common problem with the intuitive ...
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3answers
166 views
MOSFET symbol - what is the correct symbol
I've been on this site now a couple of months and I notice various symbols used for MOSFETs. What is the preferred symbol for an N Channel MOSFET and why?
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1answer
132 views
Design Considerations for a dc motor drive circuit?
I'm planning to develop a control circuit for a 24V, 500 RPM (@no load), 2A, 4 kg-cm brushed DC motor. Motor has to run only in one direction. I plan to use IRF44ZN MOSFET with a proper driver to ...
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1answer
100 views
Simplest design approach for PWM control with power MOSFET
I'm designing an application in which the current running into a load is controlled by PWM. A microcontroller generates a PWM cycle at 20kHz and this signal is used to control a MOSFET which is ...
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2answers
123 views
Why is the gate charge curve (Miller plateau) of MOSFETs dependent on Vds?
I don't understand why the gate charge curve (exactly: the Miller plateau part) of MOSFETs is dependent on the drain-source voltage Vds.
As an example, the datasheet of of the IRFZ44 shows on page 4 ...
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27 views
In what way PMOS should be interfaced with circuits? [closed]
Possible way of interfacing PMOS with some application circuit is required
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3answers
122 views
How does a dual gate MOSFET reduce Miller effect?
How does a dual gate MOSFET reduce Miller effect? I am trying to gain a global understaning of the physics behind them, not necessarily exact formula's that come with it other than maybe some for ...
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83 views
Is it important to have common ground between you microcontoller and high-power devices on the same PCB?
I noticed that there are more N-channel mostfets than P-channel mosfets on the market.
Then I realised that probably in many applications, the high powered device runs on a higher voltage and ...
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3answers
124 views
How to Power a Tank Circuit with Mosfet without the Inductor Undesireably Triggering the Mosfet
BACKGROUND: I have this circuit that I asked about in a previous question:
Someone kindly explained that the problem I'm having with the circuit is that the mosfet is being triggered by negative ...
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4answers
2k views
Are discrete MOSFETs ESD sensitive?
CMOS inputs on microcontrollers and other ICs can be damaged by ESD discharges. Can the gate of a big discrete MOSFET (2N7000, IRF9530, etc.) be damaged by ESD discharges?
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2answers
123 views
Reason for having a resistor at gate of MOSFET
If the gate current i_G=0 then what is the point in adding the resistor R1? Here is the circuit diagram:
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2answers
206 views
Question about mosfet gate resistor
I have n mosfet gate connected to 4043 logic and Id is about 100mA. Both 4043 and mosfet has +5v. I have plan to use 2N7000 mosfet
Questions are:
How large gate resistor i need between 4043 and ...
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1answer
130 views
IGBT vs. Power MOSFET for switching applications. Where to draw the line?
For lower breakdown voltages, a power MOSFET is clearly the device to go for, in view of its higher efficiency, higher commutation speed and lower price.
Where should the line be drawn, upwards of ...
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1answer
119 views
how do MOSFETS work
I understand how to use MOSFET's and build some simple circuits. What is going on inside at the atomic level where I can't see physically? I understand that BJT's work by doping semiconductors and ...
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4answers
172 views
Detect “real” overcurrent/short-circuits vs. current peaks
We have a MOSFET that drives a load. The load has a sense resistor in its current path and its voltage is used to trigger a circuit that can disconnect the load if we detect an over current ...
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3answers
322 views
Any way to use N-channel mosfet in P-channel configuration?
In my application, I need the HIGH signal to turn a device OFF and vice versa. Clearly, this is P-mosfet configuration. However, I only N-mosfet on hand.
Is there any clever way to utilize N-mosfet to ...
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2answers
117 views
Driving LED strip from microcontroller
I want to drive a strip of LEDs from a microcontroller using PWM to control the brightness. The strip I have takes about 1.5A at 12V. I'm only familiar with purely low power digital electronics so ...
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1answer
178 views
Criteria behind selecting pwm frequency for speed control of a dc motor?
I'm working on a speed control circuit for a brushed dc motor (24v, 500rpm, 2A, 4kgcm).
The main components that I plan to use are PIC16f873, 4n25 optocoupler, IRFZ44N MOSFET, BY 500 - 800 diode(for ...
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3answers
2k views
Voltage controlled current source
Here is a circuit that seems to work pretty well for allowing a voltage to control a current of up to maybe two amps.
It works on the falstad simulator (the triangle wave voltage input produces an ...
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1answer
62 views
Does this use of IR2183 as high-side n-channel gate driver work?
I'm building a switching power supply taking 12V to 19V at 3A max out. I've already built one of these using a Schottky diode for the rectifier, but this time I'm thinking of trying a ...
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2answers
62 views
Drive MOSFET from LBO output of switching regulator
Is it safe to use a MOSFET with gate connected to the low battery comparator output of this TPS61027 switching regulator in order to disconnect the load once batteries become low? The LBO is ...
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1answer
58 views
Default-on, latch-off, MOSFET power switch
I'd like to build a low-battery circuit. It should default on when first connected, but if a particular signal goes high for a small amount of time (say, 10 microseconds,) then it should turn off, and ...
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3answers
217 views
MOSFET as a switch?
In the picture shown, can "Output" be controlled to be 0V or 12V based on "Control"?
Will be Drain and Source the way it is connected be a problem?
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3answers
95 views
What material should I use to insulate my MOSFET from a heatsink?
I have a heat-sink and I want to put two FET's on it. I know I have to insulate it so the metal showing on it doesn't connect and create a path. Is there any good everyday material that would work? ...
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2answers
303 views
Isolated MOSFET output stage calculations
I am a newcomer in this wonderful world of electronics trying to design my own PLC.
So far I have designed a single output stage that I think will work, but it would be great if i could have any of ...
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1answer
163 views
Voltage regulator with op amp(negative feedback) and MOSFET
The schematic above is a very good voltage regulator, excepting the high power dissipation for Q1 (also I'd use an NPN instead of a PNP). Can I replace Q1 and Q2 with a high current n-mosfet and ...
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57 views
Depletion MOSFET
I have a depletion MOSFET that is in a common source configuration. Vdd is 10 V, 1.2 kohm Rd, 1 Mohm Rg, 0.001 uF coupling capacitors on the gate and drain. There is a load on Vout and the RL is ...
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1answer
107 views
How to switch between a solar panel and battery?
A 12v battery is being charged from a solar panel. When battery is 12v solar panel is disconnected from battery and connect the load with battery. And again solar panel is connected with battery when ...
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2answers
116 views
Confused about MOSFET
I'm using the IRF7422 (P Mosfet - warning opens a *.pdf) FETKY and I'm experiencing a strange issue.
I am pulling the gate high to +5V which should theoretically cause the source-drain channel to ...
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1answer
157 views
AVR Pin Dual Use: Input and Output at (seemingly) the same time
I have been working on a few different versions of a bicycle light control circuit which reads in various buttons and sets various outputs accordingly such as headlight, taillight, blinkers, etc.
My ...
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2answers
510 views
Calculating the pulldown resistance for a given MOSFET's gate
I searched and read many similar questions, but did not find a specific answer for how to calculate the correct value for a pulldown resistorn for a MOSFET's floating gate. Seems like everyone dodges ...
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5answers
227 views
MOSFET or Transistor for using as switch for audio signals
I was wondering which component is better for using as voltage controlled switch for audio signals (e.g. music signal from mp3 player). Should I use MOSFETs or transistors? The max rail voltage is ...
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2k views
Determine MOSFET switching speed
How can I determine the switching speed of a MOSFET, with given Qg (gate charge), Vgs (G-S junction voltage) and gate resistor ?
How should I determine the required value of the gate resistor?
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2answers
225 views
BJTs versus (MOS)FET to switch a load from a microcontroller
I would like to know what are the reasons for choosing bipolar junction transistor (BJT) versus a field-effect transistor (FET) (MOSFET or a JFET) to switch a load from a microcontroller. In our ...
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1answer
138 views
Using a single MOSFET to switch current direction
I am currently using a 30N06L MOSFET in order to control a DC engine from an Arduino using this circuit:
The problem is that this way I cannot change the direction of the engine.
Is there a way to ...
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2answers
107 views
MOSFET for PWM application
I'm designing an application where a power logic level MOSFET is driven using a 5V PWM signal at 20kHz.
The drain current will be approx. 10A and the voltage of the load 12V.
I looked into the ...
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1answer
288 views
Reverse polarity protection
I read somewhere that this can be used for the reverse polarity protection in the circuit. But I am quite confused with its operation. Can somebody help me with this.
simulate this circuit ...
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2answers
79 views
PWM controller to meet EMI/EMC regulations
I'm designing an application in which the current running into a load is controlled by PWM.
A microcontroller generates a PWM cycle at 20kHz and this signal is used to control a MOSFET which is ...
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3answers
669 views
Why won't my MOSFET work?
I am having trouble getting my N-channel MOSFET to work. I am using the MOSFET to control a DC motor. I have the the positive end of 5V power supply going to my motor and from the motor to the drain. ...
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3answers
291 views
Scaling PWM amplitude by switching an analog DC voltage?
I'm trying to make a quick-and-dirty voltage-controlled volume control circuit, using a minimal number of components.
A microcontroller is outputting two 5V p-p, 625 kHz PWM signals: an audio ...
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0answers
60 views
Matching mosfets - linear servo amplifier (AB)
I'm replacing a bunch of burnt mosfets in a linear amplifier for a brushless motor.
3 phases
Each phase: 3 pairs of totem IRFP240 / IRFP9240 in parallell. (no R in series)
My main concern is ...
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1answer
356 views
Turning a microcontroller on with a flip flop
I'm working on debugging a circuit that I've built and am trying to wrap my head around an issue.
I have the following circuit (74LCV is an inverting flip flop and the NCP1400 is a boost converter):
...
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2answers
314 views
How can I use transistors to work as an SPDT relay using the common pin as input and NC/NO as outputs?
PS: If you're impatient, you may skip to THE_POINT below:
Basically, this is for various lights in a car - indicators, park/rear light, brake light. I want to convert the simple output from ...
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2answers
119 views
Mosfets as a switch for batteries in series
I am contemplating a way to build a new battery pack for a project that I am working on. However I think that I have run into a problem, but I am not sure.
I have a battery pack with about 27 ...
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2answers
71 views
What is the definition of Cload for MOSFET drivers?
I am currently looking at the LTC4444 MOSFET driver.
It states that the rise and fall time of the gate driver for 1nF load. Is this 1nF load the Ciss value or Qg/Vgs of the MOSFET?
Thanks
