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Questions tagged [transistors]

The transistor is a semiconductor device that can amplify signals and switch power. Most used types are bipolar (BJT, for Bipolar Junction Transistor), UJT (Unijunction transistor) and MOSFET (FET, for Field Effect Transistor)

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Why is there no Phase Shift in CC and CB Configuration

I am curious why in common base and common collector configurations there is no phase shift between output and input (at low frequencies, where stray capacitance doesn't "kick in" yet)? I get it why ...
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55 views

Triode and saturation region in mosfet

What is the difference between the triode ( ohmic ) region and the saturation ( linear ) region in mosfet ?? It's confusing since both regions are linear but why does mosfet work as an amplifier in ...
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41 views

Is Adafruit's recommendation for led strip driver MOSFET incorrect?

Adafruit's article ( https://learn.adafruit.com/rgb-led-strips/usage ) states that transistor IRLB8721 can be used with 3.3V or 5V gate voltage to drive LED strip. However, in IRLB8721 datasheet ( ...
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65 views

Need help with three-stage transistor amplifier in LTSpice

I am currently attempting to design an amplifier in LTSpice for an E1 project. My professor tends to emphasize analysis of these circuits, so he hasn't really given us any kind of a design process to ...
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37 views

Problem with experiment to calculate hfe (or Beta) for a BJT

I need to calculate the current gain of a NPN BJT, and I have done an experiment where the voltage Vbe is increased slowly in steps and the resulting Ib and Ic are recorded. The voltage between ...
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1answer
44 views

How to do a transient simulation using LTspice? [closed]

I have the following circut that resembles a CMOS inverter. Now I want to do a transient simulation on this circut but I am not sure how to do it. I always get a straight line! Not sure why. I tried ...
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1answer
57 views

LED Controller + LED Panel with common cathode

I have a 3-CH DMX controller (5-24V, 5A/ch, common anode) from amazon (don't know if links are desired here) and a 12V 100W MCPCB LED panel, which unfortunately has a common cathode. The panel is ...
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1answer
91 views

Transistor current amplifier circuit

I'm trying to make a circuit that has a load resistance of 2 Ohms, load current draw of 2A and voltage of 5V. The circuit can only be fed with a 5V@500mAh battery. Here is a diagram I have thought ...
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69 views

How do logic chips (74LS, HC, …) provide output=Vcc/0V when all standalone diodes and transistors suffer voltage drops?

If you use a transistor to pull signal to high from a Vcc of 5V, signal only goes to 4.5V or so because of voltage drop over the transistor. Likewise if you use a transistor to pull signal to ground, ...
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1answer
28 views

Powering 4 modulated IR LEDs through transistor

I've done some research but can't seem to find an answer to my specific problem. I'm using an Arduino as a beam-break sensor. In order to do that it modulates the IR LED at 38kHz by code and listens ...
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1answer
21 views

Analysis of 3 Stage CS Ring Oscillator

I am new to the world of oscillators, so take it easy on me. I have been attempting to analyze the following common source ring oscillator: However, I am having some trouble here. So based on my ...
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2answers
64 views

Brake DC MOTOR circuit

I have a DC motor that is controlled with an npn transistor with pwm. Everything works fine. I want to brake the motor instantly. I tried to short the terminals with another pairs of transistors but ...
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1answer
110 views

Need help connecting PIR to LED

I have a Panasonic Pir Motion Sensor (AMN34112.) I want to connect it to a LED so that the LED lights up when the sensor detects motion. I need some help to make sure I do not destroy the PIR. The ...
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1answer
136 views

Tesla coil troubleshooting help

I'm trying to make a Tesla coil with approximately 200 turns in the secondary coil using 28 gauge enameled copper wire. My primary coil has 3-6 turns with a thicker wire. I've made all the connections ...
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3answers
54 views

Base resistor on transistor

I am new to electronics and creating my first big project but I am stumped on figuring out the value of the base resistor (R2 in diagram) of an NPN 2n3904 transistor. All of the LED are rated for 20mA....
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5answers
80 views

Does a transistor work by connecting the collector to emitter? If so, why do transistor regulators work?

I am wondering why a transistor, such as one used in this Zener diode + Transistor regulator , has the output controlled by the base voltage rather than the collector. My textbook (which has this ...
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2answers
127 views

Transistors why do they amplify current?

Ok guys I can't understand a thing of the Transistor here is the scheme: My teacher said that when I put 0,7V on the base the PN junction between Base and Collector is direct polarized so the whole ...
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71 views

BJT AC Analysis using r_e model

This is a picture of a Common Emitter Voltage Divider bias and it is been modelled using a CCCS and a diode resistance using the r_e model. Now my doubt is that I get problem in finding the input ...
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81 views

How does transistor bandwidth affect stability?

I was watching a video where Dave Jones of EEVBlog interviews Rod Elliot of Elliot Sound Products. Rod was discussing that he tends not to use digital chips in his designs because the chip will become ...
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2answers
84 views

Is my amplifier correct?

My goal was to amplify audio signal coming from Raspberry PI's audio jack, so it is louder. I have basically no clue what I am doing, but it seems to work - when I connect the speaker directly to the ...
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1answer
53 views

Need help understanding PNP Base into NPN Collecter circuit for LED Array

I am a novice in circuitry and I'm trying to make an 8x8x8 LED Cube using an instructables guide for a school project. I have ordered all the parts and was testing the grounding circuit for each layer ...
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2answers
127 views

Controlling Speaker Output with Transistors

I am awfully new to circuit design and a little confused on some of the things I can and cannot do here, so please bear with me. In a simple Arduino project, I am trying to control the output of an ...
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24 views

Blocking voltage and breakdown voltage

Is there a difference between the blocking voltage and the.breakdown.voltage in mosfet transistor ? Or the two are the same?
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1answer
82 views

Inverted Pulse Generator

How to design a circuit (only using transistors) which takes 0V to 3.3V step at the input and generates a negative 1ms pulse at the output. ...
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1answer
144 views

when a diode is forwards biased can current flow backwards through it?

when a diode is forwards biased can current flow backwards through it? this question comes from me trying to understand class AB amplifier biasing, so any additional comments about the diodes' use ...
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How do I design a MOSFET based amplifier with constraints

I am designing an amplifier using two MOSFET stages. The input is taken from a sensor and is to be amplified by a factor of 25. The output (of these two transistors) will be fed to a detector with a ...
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1answer
43 views

Input impedance of common-collector configuration

We have been asked to find the input impedance of the given circuit (above) I've done the small signal representation of the circuit which is as follows The question is : I tried to solve it i'm ...
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686 views

What is Ve in mosfet

In this curve that shows the operating regions of the mosfet What is Ve that is written Vgs +Ve ??
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42 views

BJT (Common-Collector Configuration)

As we know that for the transistor to operate in the active mode, it should have emitter-base junction as forward bias and collector base junction as reverse bias. So the common-collector ...
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1answer
71 views

Reasoning behind values of CE amplifier

I have the following circuit: I am asked to choose values for the different components such that at the end, the amplifier meets certain requirements. In the solutions, I am told that to minimise ...
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2answers
1k views

What role does this diode play?

I've just bought an Arduino Uno kit, and am going through all the projects in the booklet that comes with the kit. From even the simplest LED and resistor circuit, to get a feel for the Arduino board, ...
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1answer
60 views

Difference between driver and transistor

I asked a question earlier question, "Is it safe to run Logic ICs at their maximum output current?" asking if it was safe to run logic ICs at their maximum current. From what I understand, this is ...
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1answer
65 views

Input resistance confusion

Here's a circuit of an amplifier in the CB configuration: The small-signal equivalent is (using hybrid-pi model) I want to calculate the input resistance \$R_{in}\$. If I'm not mistaken, the blue ...
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1answer
83 views

How do actively driven mosfets or transistors react to floating source?

Attempting to add some lights to a car's "intelligent" lighting system. Want to make sure I understand how my n-channel mosfets will react to losing their ground, while their gates are still connected....
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1answer
53 views

PNP BJT small signal model

I have been solving BJT circuits on my textbook and stumbled upon a PNP BJT small signal model question. It asks to build the small signal model of a PNP transistor circuit. When I checked the ...
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2answers
115 views

How to forward the body diode of the mosfet without triggering the parasitic bjt?

For some applications the body diode of the mosfet is desired but how to make it forwarded without turning the parasitic bjt on ? The bjt's base is the body and to turn the diode on we must give its ...
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1answer
32 views

Power transistor identification

I am led to believe that this transistor came out of a (bass) woofer - one one speaker, and only one transistor (not two). This is the best photo I can get: The markings appear to read ...
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2answers
97 views

Does the body of the MOSFET consume current? [closed]

Does the body of the MOSFET consume power and pass current if it weren't grounded? Like if I had a body bias and the value of Vsb wasn't zero, so in this case the diode inside the MOSFET must pass ...
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1answer
29 views

NMOS/PMOS Transit Frequency

I found this video which shows how to plot the transit frequency in Cadence Virtuoso. But on another site, instead of using c_gg, the capacitance used was c_gs+c_gd for the ft equation. Which is ...
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1answer
63 views

Simulation discrepancy in Qucs with 2N3904 transistor

I've been testing out a few circuit simulation applications and ran into an unusual issue with Qucs and the 2N3904 transistor. For a simple NPN transistor circuit with load resistor \$R_L\$, base ...
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1answer
152 views

Arduino - Using NPN transistor as a switch to pull-up/down analog pin

Let me start by saying that I am not an EE, and my knowledge in Electronics is basic, so please bear with me and be patient if, initially I am bending a few rules. In Epee fencing, a touch is awarded ...
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2answers
54 views

Voltage readings in Transistor used as switch

I have been trying to understand the operation of transistors for a while now. Today I thought to put what I learnt into test. Cutoff operation of a NPN transistor. As I read in one of the transistor ...
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1answer
56 views

Hello, this is not my circuit. but I'm playing with it, and I have some questions

hello. First, this is not my circuit. Second, I'm newbie student. I just started studying electronic circuit two weeks ago. I'm just playing with this Circuit. just poking around.. I have some ...
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5answers
911 views

What are the limiting factors of these op-amps?

I designed a multiple feedback band pass filter ...
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1answer
35 views

Inversion Region

If one transistor in a circuit (say common source with active load) operate at the strong inversion region, should the rest of the transistor also operate on that same region? Or will it depend?
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2answers
73 views

Calculating necessary transistor for LED switching

I have only just started to play with electronics (literally less than a week ago) and have purchased myself some cheap Arduino Nano clones, as well as some LEDs, resistors (only 10 ohms at the moment,...
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1answer
45 views

Choosing transistor for amplifier

I'm going to design amplifier, requirement is that impedance for in should be more than 20kohm, impedance for out should be less than 50ohm, and voltage gain should be more than 200. So I'll make cc-...
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1answer
91 views

What's the purpose of using PNP transistors on I2S bus?

What could be the reason of using these 3 PNP transistors on I2S bus (LRCK, BCK and DATA pins)? The DAC used in this schematic is PCM5102. I know for sure that this DAC would work without these ...
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2answers
50 views

ULN2003 Saturation Voltage help

I'm busy designed a PCB that will use a Raspberry Pi's GPIOs to to drive several optoisolators. Additionally I'm also interfacing with an IO module that works with HIGH > 1V. Because of the number ...
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2answers
70 views

How much current will this LED draw?

Sorry if this is a really basic question - software engineer here, so I'm a little out of my element. I'm working on an IoT project, and I'm planning on using this button with a red LED inside of it. ...