Tagged Questions

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)

learn more… | top users | synonyms

2
votes
1answer
39 views

Bi-directional High-side NFET switches — drains or sources connected together?

TL;DR: When using two N-FETs to implement a high-side switch should the FETs be arranged so the drains are connected together, or the sources? Some additional facts about the current design: 1) A ...
0
votes
0answers
22 views

CMOS transmission gate transients

I have a question on transients in transmission gates. I've seen in a couple textbooks that the basic model is an RC circuit with a switch controlled by the control signal, and that the equivalent ...
0
votes
1answer
30 views

How is an active output clamp implemented on a high-side MOSFET switch?

How is an active output clamp implemented on a high-side MOSFET switch? If there are several possibilities, then I am focused on how it's implemented on Freescale's MC15XS3400. I can wrap my head ...
2
votes
2answers
327 views

Does this linear current source driver deliver constant current?

I was reading on LED driver designs, and I have a question about the linear current source driver. In the circuit below, will D1 ever turn off when there is too much current through R2? In other ...
2
votes
1answer
46 views

Using a MOSFET or BJT instead of solenoid

I'm trying to convert all relays and solenoids to transistors in a circuit to make it solid state. I have a small (150cc) 12V DC starter motor that is currently turned on by a small transistor turning ...
1
vote
3answers
39 views

HEXFET PWM motor driver does not work

I'm trying to drive a motor for an academic project, using the circuit in the image. The STM32F4 Discovery board that I'm using in this phase of the project produces a 30Khz PWM at 3V, that is correct ...
0
votes
0answers
39 views

MOSFET to control the sensor signal with using logic gate or capacitor

I have a problem, because I don't know which solution is better. I used two MOSFET transistors (N-channel and P-channel) to control the sensor signal. Sensor generates signals with range of 240mV to ...
0
votes
0answers
72 views

I guarantee this one will be fun - Need help putting several circuits together into one

So I did my best to annotate the schematic with what I'm trying to do. Where I'm really running into trouble is past the output of the 555. This is basically a control circuit for a camera's ...
3
votes
1answer
48 views

How to improve current control loop in power supply?

I'm working on MCU programmable bench power supply. Its range is 0-50V and 0-3A programmed in 10mV and 10mA increments. It will be published as open hardware and source code that anyone can use it ...
1
vote
0answers
52 views

Building a +/- 150V DC power supply

I'm trying to build a +/- 150V battery powered DC power supply variable power supply. I have two of these 150V nixie power supplies: http://desmith.net/NMdS/Electronics/NixiePSU.html And was ...
1
vote
0answers
48 views

MOSFET Behavior During Pulsed Operation

I am trying to use back-to-back MOSFETs/IGBTs to isolate my pulsed supply from my load. In theory, I will switch on the MOSFETs, and the pulsed supply will be attached directly to the load (but not on ...
0
votes
2answers
92 views

Calculate mosfet gate resistor?

I got this schematic : In the image you see; I'm driving two infrared leds at 40 Ma each one with a FDN327N Mosfet. Attached at D8 there is one of Teensy 3.1 digital output that has HIGH voltage ...
1
vote
1answer
61 views

High-side switch for 5V load

I need to control a 5V 60mA load from an Arduino pin, but as the load has an output (tacho) that I will be reading from the Arduino, it seems I need to connect it as a high-side switch. What would be ...
0
votes
0answers
54 views

High power LED strip dimmed by MOSFET and microcontroller

I'm planning on creating a system to control a high power LED strip from a microcontroller (probably and Electric Imp) using an N-Channel MOSFET, but I've always had a hard time with MOSFETs in the ...
3
votes
0answers
66 views

Very intermittent power MOSFET failure

I am working on a very spotty motor failure (I am not the designer). We have a wound armature which is switched by power MOSFETs. These are driven by a FET totem pole type FET driver. When the ...
1
vote
1answer
49 views

Maximum Power Point Tracking Duty Cycle for a Buck Regulator

I'm currently building a 10W high voltage (~50V-100V) Maximum Power Point Tracking (MPPT) buck regulator on the side for educational purposes. For the time being, the output is tied to a load. ...
0
votes
1answer
43 views

MOSFET Cell Balancing Circuit

I'm designing a simple cell balancing for charging LiPoFe4 cells in series. In order to prevent overcharging, when on of the cells reach the maximum charing voltage, the microcontroller will enable ...
1
vote
0answers
59 views

No output at H bridge during quick power drop

I used a H bridge with PMW control to drive DC motor in two directions. I observed a strange phenomenon that during quick voltage drop, the PWM output at M2 is cutoff, although the T4 gate PWM input ...
0
votes
0answers
26 views

What are the differences between the conventional mosfets and tunneling mosfets

I would like to know the fundamental differences in the construction and operation of Tunnel FETs and the conventional MOSFETs. Also the comparison between these two devices in terms of area occupied ...
0
votes
1answer
26 views

What does the subthreshold swing of a mosfet actually mean?

I have found several interpretations of the sub threshold swing.One is " The subthreshold swing of a device is defined as the change in gate voltage which must be applied in order to create a one ...
1
vote
1answer
55 views

Mosfet life expectancy?

How to determine the life expectancy for the given mosfet? Mosfet : IRFP460 Mosfet Datasheet http://www.vishay.com/docs/91237/91237.pdf Actual Voltage,Current and other specification. Vds = 180VDc ...
0
votes
1answer
44 views

How to Calculate Mosfet Voltages

For a N-channel Mosfet does Vds = Vdb + Vbs? Is this only true for simple models or always? Where d is drain, s is source and b is base.
0
votes
0answers
41 views

Odd MOSFET behaviour (in Multisim)

I have this circuit that's behaving in a strange manner. I am getting a surprisingly low current value flowing through the inductor when the path includes the N-channel MOSFET. Please could someone ...
1
vote
2answers
116 views

MOSFET ringing drain

Background: Using 33kHz PWM through an RF isolator [Si8710AC], to drive a power MOSFET [AUIRFZ44N], to control a high-power LED (8-10 watts). Isolator output is open-collector pulled up to +12V, and ...
0
votes
2answers
53 views

Commanding numerous motors with one H-Bridge

Is it possible to command more than one motor with an H-bridge like this: Would this work in real life if I replace switches with transistors and command them?
2
votes
1answer
78 views

Power Mosfet design issue

My schematic The components BSN20 is a N-channel enhancement mode field-effect transistor (datasheet) IRF7416 is a HEXFET power MOSFET (datasheet) This is a part of a project in which the line ...
1
vote
1answer
56 views

How does the drain current flow in a MOSFET when the channel is pinched off?

Here is what I have understood. Please correct me if I'm wrong. The depth of induced channel depends on the voltage V. Since the voltage across the gate and the path along the channel decreases from ...
1
vote
1answer
43 views

How to observe transfer characteristics of MOSFET?

I have built a simple Mosfet circuit now I want to check the Vds vs Id characteristics. But the problem is when the Vcc(Supply) and Vgs(Gate to Source) (according to the following characteristics) ...
1
vote
1answer
89 views

High side P channel MOSFET power switch - gate question, and suggestions for my circuit?

My circuit is for switching a 12V battery to a load (LED lights, designed for automotive use), during my testing with prototypes, the lights consumed about 400mA, meaning they were ~5W LED products. ...
1
vote
2answers
48 views

MOSFET current mirror: Saturation mode?

I have some trouble understanding why M1 is in saturation/active mode. According to Wikipedia a MOSFET is in saturation mode if \$V_{GS} > V_{th}\$ and \$V_{DS} \ge (V_{GS} – V_{th})\$. However ...
1
vote
1answer
68 views

OP amp voltage comparator for an FET

I have a project requiring a switch (I supply 4.8V, the switch stays off. I supply 5V, it turns on.) After some testing and asking several questions, I realized that the MOSFET I was using would not ...
0
votes
1answer
51 views

Adding hysteresis to MOSFET used as a switch

I have a low-voltage detection circuit which I use to trigger one of two LEDs (green, and red) that is powered off of a +9V battery cell. As the battery discharges, its output voltage decreases, until ...
2
votes
1answer
88 views

Mosfet Snubber with Inductive Load

I am designing switch circuit that switches on and off a relay that switches on and off a 115AC light.So the switching speed is not a concern as it is a once in a while on or off. The relay for the ...
3
votes
1answer
112 views

Brushed DC motor control MOSFET selection

I want to control a brushed DC motor of the below specification: Motor: Permanent magnet DC brushed motor Voltage: 180V Current: 5 Amps RPM: 1500 The control method is PWM switching through a ...
0
votes
1answer
75 views

MOSFET based H-Bridge Circuit

Okay really need help on constructing a MOSFET based H-bridge circuit with a switch. I've got two p type and two n type mosfets. I understand you have to apply voltage to the gates to turn the ...
1
vote
1answer
60 views

Gate Source Voltage Drop Approximation

When dealing with BJTs in an approximate large signal analysis, Vbe is often chosen to be 0.7 Volts (Given the component is operating in active mode). My question is: Is it possible to do the same for ...
1
vote
2answers
82 views

Replace mechanical switch with transistor? MOSFET? Relay?

If I have a switch in some consumer electronics that I take apart, and want to replace a mechanical switch with a digitally controlled one, which component should I use? The only problem I see with ...
1
vote
1answer
86 views

MOSFET threshold voltage and body effect

I'm trying to simulate a common drain amplifier on LTSpice which can be used to shift the input voltage either up or down by the threshold voltage (\$V_{IN}+V_{TH}\$ or \$V_{IN}-V_{TH}\$, depending on ...
1
vote
2answers
99 views

PFET to turn on/off system power

I have a Raspberry PI board connected to some external circuitry, and am using Microchip MCP23008 I2C GPIO expander chips to control external LEDs and motor circuitry. One important part of this ...
0
votes
1answer
32 views

Is IRFD 014 an appropriate FET for switching an array of (about 40) UV LEDs?

We have an array of UV LEDs. The LEDs are rated at 3.2 V – 3.4 V at 20 mA, and we plan to use a 5 V supply for simplicity. We will be using a dedicated 100 Ω resistor for each LED (the power ...
1
vote
2answers
251 views

How to make a 12V DC variable voltage supply with more than 30A output?

I have a SMPS capable of outputting 33A at 12V and I would like to make it have a variable output with full current potential, or close to it. Now, Is it possible to do it with a PWM-controlled ...
0
votes
1answer
69 views

Adjustable charge current from programming resistor for Li-Ion charger - how to change on demand?

I am designing a device which has an integrated Li-Ion battery (single cell, for simple low power portable digital device) and normally charges by way of a buck converter which goes from 12-16V ...
1
vote
1answer
49 views

Flyback converter current flow?

If you look at the flyback converter circuit above, the current only flows in one of the coils at any instant of time. What stops the magnetic field generated by the coil in series with the MOSFET ...
0
votes
1answer
56 views

Simulating a circuit consisting of MOSFETs

When simulating a circuit consisting of mosfets, when can you say that the MOS should be in cut-off, saturation. or linear (triode) region? Specifically a charge pump circuit utilizing PMOS.(refer to ...
3
votes
1answer
111 views

Do AC inverter H bridges ever get driven this way?

There's a google competition going on at the moment called the little box challenge. It's to design a very efficient AC inverter. Basically the inverter is fed a DC voltage of a few hundred volts and ...
0
votes
3answers
83 views

How hot can MOSFETs get before blowing up?

This is different from a lot of other stuff here, but I have a motherboard that has no MOSFET cooling, and when I touch them they burn my hands; they are probably 70-80C. I just want to know how long ...
0
votes
1answer
90 views

Homemade Brushless ESC

I am currently working on building a quadcopter with brushless motors. I decided to try to build the ESCs by myself with some MOSFETs. I am using an Uno as the main controller on the receiving end. ...
0
votes
0answers
28 views

Mosfet amplifiers mismatch effects comparison?

In Mosfet amplifiers we have Rd mismatch effect and gm mismatch effect .Which mismatch has the biggest,most important effect?
1
vote
0answers
43 views

Preference of MOS resistor as load in MOS inverter [closed]

Whys is a MOS resistor preferred over diffused resistor as load in design of a MOS inverter?
2
votes
2answers
87 views

Push-Pull driver for low side mosfet — is it a good idea?

I want to build an H-bridge to control a 36V dc motor (or possibly 48V but lets stick to 36V for now) The electronics that will control the H-Bridge (logic, etc) will run from a 12V ...