Field Effect Transistor, a transistor in which most current is carried along a channel whose effective resistance can be controlled by a transverse electric field. Commonly used types of FETs include the Metal Oxide Semiconductor FET (MOSFET), and less common in recent designs, the Junction Gate ...

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48 views

Mosfet won't turn fully on

I have a IPB011N04LG N channel MOSFET configured as a switch in the following circuit: It works, but doesn't turn fully on. If \$V_{\text{BAT}}\$ is \$23\$V I get \$11\$V on the load side If ...
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1answer
38 views

Getting bad clipping issues with this 3 stage amplifier

What am I using? 3 stages of amplification. An input voltage of 10mV peak or 20mV pkpk into the first stage. 1st stage: NJFET Common Source. Using a voltage gain of 3. 2nd stage: NPN BJT Emitter ...
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2answers
45 views

Designing a MOSFET current mirror circuit

This is the design problem: This is a brief of my design for W and L of the transistors and R: I've connected the upper voltage source to ground and made the lower one equal to 0.4 V to make ...
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1answer
86 views

Why does the datasheet for this FET show two / three VGS(off) values?

I am using a MMBFJ270 P-Channel JFET and if you look at the characteristic graphs it is saying that there are two values for VGS(off) and in one graph it quotes three different values... Why does it ...
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0answers
36 views

P-Channel FET Switching Time

I have a question about the circuit shown below. Specifically, I am looking to calculate the time that it takes to fully enhance the PFET and activate 3V3_SW1 after the control signal transitions ...
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1answer
89 views

What are the resistors in digital pots?

Do they place tiny switches with passive resistors or are they using fets in the ohmic region ?
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1answer
46 views

Discharge of a load capacitor through a cascode

How will a cascode effect the discharge of the load capacitor? I would expect that the discharge trough the cascade is slower since the cascode has higher output impedance. simulate this ...
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2answers
479 views

Choosing and biasing a MOSFET controlled by a microcontroller, does current matter?

I need some help choosing a MOSFET for the circuit that I described here, which I originally designed using a BJT but decided that FETs make more sense in this case. The FET will be controlled by a ...
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3answers
103 views

What precisely is \$R_{ds(on)}\$?

I keep getting conflicting answers on this and it's absolutely killing me. Some say \$R_{ds(on)}\$ is the contact resistance in the FET (for instance, make many FETs of varying channel lengths, turn ...
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1answer
89 views

Battery Discharge

I am making a circuit to discharge an 18V Li-ion battery, with multiple cells, in order to condition it. Each 18V cell has a capacity of 100Wh when fully charged. I would like to control the condition ...
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1answer
53 views

Switching using FET [closed]

I need a FET/MOSFET that would trigger switching at 0 - 5v. A voltage of 1V will be supplied to gate. What FET/MOSFET could I use? A specific FET. This is for our thesis and this is the only part I ...
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0answers
36 views

Noise in FET in comparison to transistor

Noise is an important feature in FET. Why noise is less produced in FET in comparison to transistor?
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1answer
142 views

I need helping understanding this VCO circuit

The two circuits of interest are described in pages 12-14 of Texas Instruments' Application Note 263, Sine Wave Generation Techniques PDF WARNING I'm primarily concerned about the circuit in Fig. 15, ...
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0answers
83 views

adjustable current driver for high power LED

I am trying to driver 3 high power RGB LED "Edixeon RGB" I want the current to be able to vary from 0 to 350 mA I am using three classical linear circuit, one for each color, with a current sensor ...
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vote
1answer
123 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 ...
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3answers
134 views

Recognising output impedance of an amplifier though inspection

The output impedance of FET amplifiers seem to be a hit and miss affair when I try to find it just through inspection. For example, sometimes it's easy to predict, whereas some other times I have to ...
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0answers
42 views

Motor Driver signal

As I was taking some screen captures of the FET's drain, to ensure the back EMF was indeed within specs, I noticed my signal was not pulling to ground when the MCU would switch it off. The capacitor ...
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votes
1answer
131 views

Question related to Cascode Circuit

I am trying to solve the following question related to cascode circuit. Where T5 has Vbe=0.7V I have answered the questions as follows. - Explain how the circuit works? The circuit has a DC ...
1
vote
1answer
49 views

How to determine FET switch specifications

I am working on a DIY drone, and I (preferably) need to be able to disconnect my ESCs from the battery via the transmitter (a Raspberry Pi). After looking for solutions for a while, I concluded FET ...
0
votes
1answer
393 views

Which kinds of FET have a body diode

I need to detect small high and low peaks in the battery voltage while in use. The goal is to help estimating the end of the battery charge by its change in impedance, since my circuit uses the ...
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1answer
130 views

characteristics graph

I'm currently learning about Field Effect Transistors in my college class. And I'm having trouble understanding how to properly read characteristics curve graphs. I'm sure it's relatively simple, ...
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2answers
195 views

the circuit of active probe using FET trace CRO [closed]

pls suggest the circuit of active probe using FET trace CRO.
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0answers
114 views

Switching between external 5V and Power over Ethernet

I have a project that should control WS2812 LEDs, and use the strong 5V supply for the LEDs for its power (using an Allegro A4490 to generate 3.3V, 2.5V and 1.2V). Now I'd like to add a relay to ...
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3answers
113 views

Audio FET Buffers and Negative Feedback

I am struggling to come to term with how negative feedback helps widen the scope of input signals coming into FETs (or OpAmps for that matter, but I am using J201 JFETs). I am aware that the largest ...
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4answers
2k views

FET vs bipolar junction transistor

I know this question might sound obvious, but still I cannot find an answer. What is the purpose and best-fit applications for field effect transistors? I mean, we have bipolar junction NPN ...
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1answer
120 views

What do \$V_{TN}\$ and \$V_{T}\$ stand for in a MOSFET?

What is the meaning and difference between the symbols: \$V_{TN}\$ and \$V_T\$ commonly seen when talking about a MOSFET? I'm guessing \$V_{TN}\$ is the threshold voltage, but what is \$V_T\$, and ...
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2answers
158 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 ...
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votes
1answer
89 views

load switch capacitance constraint

Considering using a Load Switch like DigiKey FDC6330LDKR-ND for powering on and off a device at the far end of a cable. The voltage and current requirements are well within spec however load ...
2
votes
2answers
630 views

What's the most efficient way to derive negative voltage for a bench power supply?

I’m building a bench power supply based on two LM317 with the following specs: Input: 127VAC (from mains) Output: adjustable from 1.25VDC to 15VDC Current: limit adjustable from 100mA to 1.5A In ...
6
votes
4answers
9k views

Best transistor to use for audio amplifier

This term, we will be designing an audio amplifier. So far in our lecture, we are still at BJT and based from what I've heard, FETs will just be partly discussed unlike the thorough one on BJT. ...
2
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3answers
496 views

FET electrostatic damage

I have read that electrostatic charges produced by human body can be as high as up to a several thousand volts. How exactly damage of transistors happens MOSFET NPN Electrostatic voltage applied to ...
4
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2answers
127 views

Is there a standard way to implement desat protection on high-current FETs?

To implement desaturation protection on a switching transistor, one typically sets some manner of comparator to watch the voltage across the current flow terminals of the device. If that voltage ...
2
votes
3answers
310 views

Energy harvesting - drain capacitor when voltage is reached, ultra low power

I want to connect tiny solar cell to a capacitor, let it charge it and once voltage reaches 2V - flush it through tiny red LED. Could anyone suggest how to implement that given that charge current ...
2
votes
2answers
383 views

FET - Source follower utilizing current source to lower voltage offset

I understand that if I use a FET as a source follower, the signal will be slightly attenuated due to the fact that there is some small inherent resistance in the FET, creating a voltage divider effect ...
0
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2answers
143 views

Switching a circuit from an I/O

I have an audio amplifier that draws about 200-300mA max that I would like to switch on/off using either an I/O line or a the switch pin from the headphone connector. I was thinking about using an npn ...
4
votes
1answer
439 views

3 terminal 5V high side load switch with 3.3V control

So I wasn't thinking very hard when I designed a circuit to selectively power the analog portion of my design and ended up with this: simulate this circuit – Schematic created using ...
4
votes
1answer
122 views

Safely detecting presence of 12v applied via exposed terminals for use with microcontroller

I have a board which contains a microcontroller and a 10k NTC thermistor (B57421V2103J62) wired to two external terminals, one of which is common with the board ground plane. The terminals are exposed ...
3
votes
1answer
170 views

Transistor part number selection software

I know there are online/offline softwares for finding equivalents or known transistor datasheets but is there any software that works inversely? For example that I can ask the software for a ...
0
votes
1answer
286 views

FET with high current ( power JFET) low VGSoff

I am looking for a N- channel JFET part number with IDmax > = 800 mA and low VGS(off) < -15 volts. I dont focus on the frequency As an inherent charactristics of JFETs is high working frequency ...
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2answers
398 views

How to control the gain of FET/BJT/Op-Amp amplifier by input voltage range?

Assume I have an input voltage ranging from 5-10 MHz and want to amplify it. The case is pretty simple as any device as FET,BJT or high frequency op-amp can do the amplification well but I have a ...
1
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2answers
1k views

FET impedance converter (for a non FET electret mic)?

I have a few Electret Microphones (KEAG45NPF-W). But these are all without a FET. The data sheet tells me i need to add a 'FET impedance converter'. Now, i'm still learning, and i have very basic ...
2
votes
1answer
85 views

Power dissipation in Fets synchronous switcher

I'm working on a design that includes a synchronous buck switching regulator and I've been trying to understand how much power each FET will have to dissipate. I've been looking at different ...
3
votes
4answers
659 views

N-Ch FET with open-drain output

I stumbled across this line in this datasheet (page 10): Serial Data Output Pin. Internal N-Ch FET with open-drain output that requires external pull-up resistor. It shifts out the previous ...
6
votes
2answers
801 views

Switching Between Two Voltage Supplies

I have been trying to work out a circuit something like the following: simulate this circuit – Schematic created using CircuitLab I want VOUT to be 3V when the switch is open and 5V when ...
1
vote
1answer
114 views

Turning the PN junction of JFET on?

I am going to use a N channel JFET as a normally-ON switch. I am wondering if it would cause any problem in the long term reliability having the PN junction forward-biased. In other words, would it be ...
6
votes
3answers
5k views

What can cause a Drain-Source short in a FET?

Background: I am using a Si7456CDP N-channel MOSFET in a switching power supply. The power supply and load are housed in a plastic enclosure. Yesterday, the power supply and load were working ...