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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2answers
77 views

is a uA current FET or BJT circuit design possible?

I'm working on a battery powered circuit that is triggering an interrupt on an ic with an internal pull-up. The resistor value and normally closed switch can not be changed. The quiescent current is ...
-1
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1answer
93 views

Can I modify this FET board to the ground leg instead of the VCC leg (see image)

Please see if the modification I have made to the FET switch board looks workable. See image attached. And I know it doesn't look like but the Drain is connected to VPP in the modified schematic. ...
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2answers
44 views

Output characteristics of power transistors

The book about electronics that I'm currently reading only briefly mentions IGBTs and power mosfets(such as the VMOS, or the HEXFET), and gives no depiction of the output characteristics. The image ...
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2answers
52 views

Depletion P-channel JFET that's saturated at \$V_{GS}=0V\$

Is there any depletion-mode P-channel JFET that is saturated at \$V_{GS} = 0V\$?
1
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1answer
115 views

FET-based voltage regulator with TL431

I'm looking for some help with understanding (in fact, correcting or confirming my understanding) of how the following circuit works: U1 here is TL431 voltage regulator, for example from Texas ...
1
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3answers
50 views

FET device parameters explaination

I'm looking for a FET device to use as ON/OFF switch. I've found for example this device: http://www.vishay.com/docs/62903/sis990dn.pdf I need to find a device that can handle on Source-Drain up to ...
0
votes
2answers
68 views

FET atmega168 - transistor needed?

I'm trying to make a BLDC controler, and I'd like to use an atmega168 as microcontroler and N-FETs (x3) to control the motor. The microcontroler will output a PWM that will control the motor's ...
2
votes
6answers
174 views

Would it be possible to make a solid state transistor by hand?

I am curious, would it be possible to fabricate a modern BJT/FET transistor with hobby/garage tools only if size and aesthetics was not important? Which materials would one use and how would one ...
2
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1answer
76 views

Very odd open-drain output design

I ran across a open-drain design and am baffled by the resistor between the nFET source and ground. There are only two purposes that I see it could serve. 1) It's series source termination, matching ...
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2answers
83 views

Puzzled by FET circuit

simulate this circuit – Schematic created using CircuitLab At a coffee house recently, I saw a napkin drawn schematic at the table before the waitress cleaned up after the previous ...
0
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0answers
38 views

Driving solenoid with Microcontroller with variable strength

I am working on an interface to trigger physical drums with solenoids. Therefore I need to not only drive the Solenoids Hi/Low, but also change the force - ideally using PWM for each individual ...
2
votes
1answer
118 views

JFET biasing problem

I tried solving this problem, however I feel like there's something missing, I am asked to bias a N-channel JFET with using this provided data: Idss= 12 [mA] VDD= 12 [V] VP = -5 [V] VDS=VDD/2 ...
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1answer
54 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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votes
1answer
53 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
84 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 ...
5
votes
1answer
118 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
44 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
95 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
63 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 ...
8
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2answers
554 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 ...
4
votes
3answers
110 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 ...
1
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1answer
123 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 ...
0
votes
1answer
62 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
40 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
220 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
102 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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1answer
142 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
155 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 ...
0
votes
0answers
43 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 ...
3
votes
1answer
138 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 ...
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1answer
57 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
689 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 ...
0
votes
1answer
180 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
224 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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3answers
129 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 ...
5
votes
4answers
3k 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 ...
1
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1answer
130 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 ...
0
votes
2answers
176 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 ...
2
votes
1answer
118 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
763 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
12k 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
votes
3answers
600 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
votes
2answers
165 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
338 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
448 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
votes
2answers
151 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
540 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
128 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
186 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
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1answer
325 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 ...