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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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
89 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 ...
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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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148 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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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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1answer
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
121 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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2answers
121 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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1answer
127 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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116 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
169 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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202 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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2answers
114 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
160 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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1answer
128 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
55 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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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
59 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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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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3answers
207 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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1answer
153 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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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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117 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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1answer
153 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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5answers
219 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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135 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
219 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
99 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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106 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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2answers
78 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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59 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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2answers
117 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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86 views
Level shifting with BSS138 - weird values
I need to connect 5V and 3.3V devices via I2C as follows:
I've connected 3.3V and 5V pull-ups and try to measure voltage. There is 5V on HV and TX_HV but 4,7V on LV / TX_LV.
Putting TX to LOW ...
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290 views
Why do I have to use the same ground?
I've connected an Arduino to a MOSFET to control a valve.
I've connected the Arduino's GND to the negative lane (word?) on the breadboard (for clarity modeled by SW1 in the circuit diagram).
I ...
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1answer
84 views
Power switching a higher DC supply from a mcu
I'm designing a pcb with a 3.3v mcu and some 5.5++V modules on it.
My microcontroller is doing the power-management, turning the 5.5V supply on/off. But I'm not sure how to turn the "high" voltage ...
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308 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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5answers
222 views
OP amps with output on N-channel MOSFET
I need to analyze a schematic and I am having trouble with this part:
The thing is I don't get at all the utility of the N-channel MOSFET at the output of the op-amp. Could anyone explain the ...
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2answers
209 views
Simple MOSFET switch question
I have an application where I want to pass a current of about 300mA through a load, which should be turned on/off via a 3V/0V signal. I thought of using a 2N7000 as the switch and have it set up on a ...
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67 views
MOSFET Common Source Analysis Basics
I still don't seem to understand the basics of MOSFETs, I was looking over this slide from a lecture but I don't understand how the gain was solved for.
Can someone explain to me how the gain was ...
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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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2answers
152 views
Signal volume LED Array
I am done a google search on this and have come up blank. What I have is a signal/sound being fed through a wire that ranges from (0-9V). When the volume is low, and i need 1 or 2 leds to light up, ...
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279 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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68 views
I am searching for a MOSFET having these characteristics
N channel
Frequency Range: 100 Hz to 1 MHz
Mid band gain = 200
Please help me.
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1answer
137 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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103 views
Is Rg, calculated in the linked PDF calculating the pulldowm/pullup resistor for a MOSFET gate?
I stumbled upon the following paper while looking for ways to calculate a specific value for the pullup/pulldown resistor for the gate of a MOSFET. I see several calculations for Rg. Is that the ...
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166 views
Wiring an illuminated toggle switch
I'm trying to build a model rocket launcher circuit. So far I have
this
The igniter requires 12V and 3A, BAT1 is 12.6V 9800mAh.
The arduino input pin should read HIGH when the igniter is connected ...
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120 views
Solid State Switch for magnet DC Generator
I'm using a flywheel-driven permanent magnet DC generator to charge up a bank of supercapacitors, 35 farad rated to 25V. For safety I limit the max charge to 22V via a comparator and a zener ...
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487 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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Saturating a N-Channel MOSFET
I have created a schematic for a circuit that I wish to create. I believe the underlying circuit is pretty solid; however, I am having trouble picking parts with the right specs. I have attached the ...
