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

1
vote
0answers
31 views

Can BJTs operate in the nano-ampere range?

Can BJTs can operate predictably with very low currents, in the order of nano-amps or less? I am involved in microelectronics design and have made a voltage reference chip that is MOSFET-only and ...
1
vote
2answers
48 views

Analog Fan control via PWM

I want to control a fan using analog voltage instead of PWM. I have a PWM signal from MCU. I want to use a low pass filter to convert this to analog, so 0 to 3.3V based on PWM duty cycle. This will ...
1
vote
1answer
50 views

How do I calculate the max pwm frequency my h-bridge can handle?

my configuration: H-bridge with 4 n-ch mosfets (IRF1405) with a gate capacitance of 5480pF and turn on delay time 13nS. I am ...
1
vote
1answer
25 views

Latch power on-off circuit

See the circuit below: I am trying to make a shutdown circuit for a low power application. Basically, I want the system to be able to be turned on by a button push, and then turned off by a ...
1
vote
0answers
17 views

Switching cold cathode fluorescent lights on and off without relay?

I have a few sets of 2-in-1 CCFLs that are designed to be powered off the 12V rail of a computer PSU. I'm planning to build a large 7-seg display using them so I'd like to be able to switch them on ...
0
votes
1answer
27 views

n-type mosfet calculate AD AS PD PS

I have a nMOS and I want to calculate AD AS PD PS . Given: L=0.25μm and W = 2μm. We know that \$AD = W*L_D\$ and \$PD = W + 2*L_D\$ ...
0
votes
2answers
130 views

What's the best MOSFET for switching small currents?

What are the most important characteristics to look for in a MOSFET for switch a precision 50nA load? The MOSFET should be able to switch the load on or off within 1us. The overshoot/undershoot ...
0
votes
0answers
38 views

How to deal with asymmetrical slew rate in 2-stage op-amp?

I made sure to take slew rate into account when designing this op-amp, but the slew-rate appears to be asymmetrical, as apparently the fall time is much slower than the rise time. How do I rectify ...
0
votes
2answers
65 views

How to choose optimum length for op-amp design?

I've heard that minimum length is discouraged in analog design due to matching problem but what's the drawback of using very long transistors apart from the size and resistance? Based on the ...
0
votes
1answer
37 views

Any good resource for MOSFET op-amp design? [closed]

I've been trying to design a two-stage op-amp for a week, but I haven't been progressing much. Does anyone know good resources that teach you how to design an op-amp (transistor level), preferably ...
2
votes
1answer
63 views

How do you calculate ICMR?

Let's say the Vdsat = 0.2V for M1 to M4, but 0.5V for M5. VT is 0.5. I think it's: ...
2
votes
3answers
87 views

NE555 Flyback Driver MOSFET failiure

simulate this circuit – Schematic created using CircuitLab I made this simple NE555 Flyback driver. I used a 9V Battery to power the NE555 and a 24V 6A power supply to power the flyback. ...
0
votes
1answer
68 views

What determines the operating point of an op-amp?

Let's say I have the following 2-stage op-amp: The DC transfer is as such: I would like the slope to be steeper and the center point to be at 0mV input. What should I be changing? In other ...
0
votes
2answers
61 views

Why I can't get a clean signal from my opto-isolator?

I am trying to get working my first Mosfet H bridge. My H bridge characteristics are: 12v power supply 3.5A max current I need to control the bridge from a microcontroller 5V output About 30KHz PWM ...
1
vote
1answer
42 views

Using p-channel mosfet on high side of h-bridge, do I really need a driver chip?

I know there are fancy h-bridge ic's to drive high side of h-bridge but I guess that is when I have to drive n channel mosfet. I am planning on using p channel mosfets on high side and n channel ...
1
vote
1answer
63 views

Why doesn't a capacitor connected to a MOSFET charge to VDD

If an nmos which has the gate and drain connected to VDD, and the source connected to a grounded capacitor, the nmos will start conducting and the capacitor will start charging as long as VDD > VTn ...
1
vote
2answers
87 views

PMOS Inrush Current Limit - Where to place Capacitor

In order to reduce back-EMI of a Buck converter a LC input filter is to placed in front of the converter. To limit the inrush current when those caps are charged I consider to use a PMOS with a RC ...
1
vote
1answer
23 views

Cadence, BSIM3V3, and the Body Effect

I am trying to meet the compliance/min output voltage of a wide swing current mirror so the output current (10uA) is within .1% or +/- .01uA. I am using Cadence and ami06 nFET's to do so. I am always ...
3
votes
3answers
271 views

on-going quest to understand p-channel MOSFETs

(Disclaimer in case it isn't painfully obvious - I'm very much a n00b, especially when it comes to understanding transistors). I thought I had it all figured out - a p-channel MOSFET is (or can be ...
0
votes
1answer
71 views

Replacing BJTs with power MOSFET

I have 2 x 2N2222 BJTs powering 2 relays of 200mA each. I am using 2 output pins with 500ohm resistors to power the transistors. After powering it the circuit not working well, while replacing the ...
0
votes
1answer
57 views

Reduce discrete linear voltage regulator dropout

I am investigating the following circuit taken from here which works fine in simulation. However, while Vout rising linearly with Vin it shows a ~800mV dropout, which I don't quite understand. ...
0
votes
2answers
79 views

Which is better as a switch? [duplicate]

The offset voltage of a saturated transistor, makes bjt less attractive as a switch than mosfet. Why? Is there any other logics aside this?
2
votes
1answer
58 views

Does this H-Bridge need any supporting circuitry?

I'm still pretty new to transistor stuff, so excuse the n00b question. I'm looking to use this h-bridge to toggle a latching solenoid valve, where I need to toggle it on/off with +/- 6VDC. I've used a ...
2
votes
3answers
188 views

MOSFET and 3 V power supply

I want to control an N-channel MOSFET from a 3 V power source. The thing is, I have difficulties understanding how to know the minimum Vgs value is to be applied for the MOSFET to be saturated. ...
1
vote
2answers
73 views

Can I use a dual high-side low-side gate driver as a dual low-side driver?

Some background: I am building a 350 VA DC to AC inverter, partly for my own curiosity, but mostly for a senior design project for my bachelor's. What I have with me is monolithic dual high-and-low ...
1
vote
2answers
74 views

PMOS Turn-On due to gate capacitance?

I just stumbled over a quirk in my simulation. I have a fairly standard PMOS gate drive with a capacitor C1 for controlling inrush current during turn-on. EN input is normally high and pulled low ...
1
vote
1answer
51 views

Leakage from MOSFET Switch To Ground

I built this circuit at home to for science (I explicitly drew the body diodes for clarity). simulate this circuit – Schematic created using CircuitLab Imagine the following scenario: ...
0
votes
1answer
114 views

Stacked MOSFETs

Will the following scheme work if one of the lockout gates are energized? Or another way of putting it, can the normal operation of a MOSFET be achieved by the connection and disconnection of the ...
1
vote
1answer
42 views

From curves to SPICE model

In the lab I measured the Vgs x Id and Vds x Id curves of a MOSFET transistor (actually, the CD4007 IC that has 3 PMOS and 3 NMOS transistors within). How would I go into turning this data into a ...
1
vote
1answer
105 views

Do N-channel MOSFETs require a pull-down resistor?

I'm using an N-channel mosfet to supply power to a servo. The problem is that even with the gate set at low, I'm still getting some amount of voltage (~0.9V in a 5V system) coming through. Do I need a ...
0
votes
1answer
68 views

how to cut off power from usb device using arduino

Seems like I can't restart USB modem in Linux, so I setup an arduino gig to emulate usb modem plug/unplug. I have Arduino Uno R3 and several N-channel mosfet https://www.sparkfun.com/products/10213, ...
0
votes
2answers
124 views

Transistor to run relay

In addition to my last post I have more information and details. I want to run 240V Relay (5V Coil) from my AVR chip (ATmega328P). My EMR relay takes up to 200mA on it peak. I have 2N2222 ...
0
votes
1answer
73 views

Long wire PWMed LED lights

so I plan to build a house (at some point in future) and I'd like to implement some sort of home automation. Now one of the things I'd like to have is PWMed lighting. Most of the lights would be 12V ...
1
vote
3answers
102 views

How do I drive a MOSFET working under high voltage while keeping it insulated from the rest of the circuit?

I want to drive a MOSFET with a 50Hz, 50% duty cycle clock pulse. The voltage to be switched is as high as 300V DC. The section inside the dashed lines will stay electrically isolated from the rest ...
5
votes
1answer
233 views

Does MOSFET let current flow through source to drain as it allows it from drain to source?

Does a MOSFET allow current flow in reverse direction (i.e.; from source to drain)? I made a Google search, but couldn't find a clear statement about this matter. I have found this similar question, ...
0
votes
1answer
49 views

LiPo Battery: series to parallel charging switching circuit

simulate this circuit – Schematic created using CircuitLab So, I have two 2000 mAh LiPo batteries that are going to be powering a GSM modem (on an arduino shield) a GPS and a motor. I ...
0
votes
1answer
58 views

How to use MOSFET thermal data for simulating in software

I have a MOSFET (irfb7434pbf) acting as load switch in a circuit. The usual operation is well within the SOA region, but, on situations where the load would short circuit, the MOSFET is set to limit ...
0
votes
1answer
57 views

Real-life discrete monoflop

I my current project I need a high-side PMOS to disconnect a load once a over-current or (downstream) over-voltage condition is detected. Obviously without a permanent latch, once the PMOS opens, a ...
0
votes
1answer
38 views

Low Current Battery Montior Detail Question

I'm trying to design a circuit that will be running from a battery. I'm currently working on the part that detects the voltage and came across this question (and answers) here: It made pretty good ...
1
vote
1answer
88 views

How does the PWM from MCU get translated into a output voltage as in Power Electronics [closed]

Background: I am preparing for a full-time employment starting in May. I am coming from a computer engineering background so I only have some working knowledge regarding EE. The job duty is Firmware ...
3
votes
1answer
69 views

Li-po Charging circuit question (switching between battery and power supply)

I'm building a circuit containing a Li-Po battery and a battery charging chip. I do understand the working of the chip, but don't really get how to switch the system load to a normal power supply ...
0
votes
2answers
106 views

Debugging a garage door opener circuit with an optocoupler and mosfet

There seem to be many related questions, but I can't quite find the answer I'm looking for. I've got a garage door opener switch. There's 16V across the wires, and when you short them, the garage ...
0
votes
3answers
70 views

Voltage dip on MOSFET switchable current shunt

I have the following circuit built up in LTSpice which will be used to switch in different sense resistors for current measurements. The mAEn signal switches the M1 transistor on at t=10ms which ...
-2
votes
1answer
57 views

Uprating for the MOSFET

How good is it to uprate FET device to exceed the 150C junction limit absolute? What are the critical parameters to look for when uprating FET device? Thanks. Vic
0
votes
2answers
68 views

struggling to use MOSFETs as switches: is the problem my circuit or the choice of mosfet?

We are using an arduino to selectively apply 5V to the gate of MOSFETs, with the intention that current will only be allowed to pass through our solenoid from the supply in the situation where both ...
0
votes
2answers
55 views

N-Channel MOSFET Selection - SOA & determination of VDS - LED Application

To begin, I've thoroughly searched for answers to my question/s and have yet to find any clear & concise data. I'm in the progress of determining an appropriate N-Channel MOSFET to be used as a ...
0
votes
1answer
68 views

zvs induction heater mosfet failure?

Hey guys my name is Barrett I'm an electrical engineering student and I'm new to the forums. I've been super excited to put a zvs induction heater together and I finally got all my parts turned it on ...
5
votes
1answer
273 views

Why Vds increase slowly even if it decrease fast?

The schematic is The wave form is as follows, yellow line is channel 1 which is gate voltage and blue line is channel 2 which is drain voltage. The 148kHz PWM signal is totem pole output of ...
1
vote
3answers
143 views

Proper usage of a MOSFET to control USB

On the RaspberryPi.SE it was suggested that one can use MOSFET BS170 to switch a USB device on and off by a GPIO pin (3.3V). I need to get 500mA to power a GSM dongle; the voltage drop should ...
3
votes
2answers
370 views

How do I make an LED turn on when my output reaches 5v?

I'm a hobbyist and pretty new to many of the components involved, so I hope you guys can help me here. I'm trying to keep the circuit as simple as possible. I made a small variable power supply with ...