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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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Help me to identify this transistor (PIC inside) [closed]

Hi @can you help me to indentify this transistor of my old EVGA X58 SLI (132-BL-E758-E1)? It's something related to the system temp sensor, because the "system temp" sensor its faulty. The transistor ...
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51 views

Bipolar transistor. Unknown graphs

I read a course about power transistors and I encountered these graphs The chapter is talking about safe operation of BJT. Can anyone tell me what those graphs are ? (And how to read them).
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72 views

Pausing a clock signal generated by 555 timer

I am planning to make a simple integer adder/multiplier which needs a variable frequency, comparatively slow clock (around 1 to 200 Hz) for demonstration purposes. I used the following generic 555 ...
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1answer
30 views

Hooking into Qi charger status LED to power something more

I have a Qi charging module and I want to light up a higher-power string of LEDs when my phone is charging through it. The module has a blue status LED to show it's charging, which I think is where ...
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1answer
41 views

High(er) Current AC Flasher Circuit

I'm trying to develop a flasher circuit for an aircraft warning light like the one shown at https://flightlight.com/products/obstruction-lights-controls-faa-l-810/. The light will be powered with ...
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43 views

P-Channel MOSFET not behaving as expected

I bought some IRFD9024 p-channel MOSFETs, and for some reason there seems to be a diode drop from the SOURCE to the DRAIN. As far as I understood it, the body diode is from the DRAIN to the SOURCE as ...
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81 views

How to amplify current and buffer voltage

I have a battery supplying 5V@500mAh and an LED (the load) which draws 1000mA@5V (twice the current the battery supplies per hour). I found some circuits that have NPN transistors only and other ...
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1answer
71 views

Questions About BJTs in My Circuit

I have an LED multiplexer circuit (inspired by https://www.instructables.com/id/Multiplexing-with-Arduino-Transistors-I-made/) in which I have set the resistor values to maximize the current through ...
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1answer
149 views

What's wrong with this single-transistor level-shifter?

I was trying to step up the output of a 3.3V microcontroller pin to 5V for communication with another device. I wanted to do it with a single bjt, and found a good design for doing that here Single ...
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61 views

Determining the output resistance of a BJT amplifier

I'm given the following amplifier: (all the transistors have the same characteristics; Early effect is neglected) In order to calculate \$R_{out}\$, we replace the circuit with its small-signal ...
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4answers
307 views

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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1answer
258 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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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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73 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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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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72 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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189 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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73 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
33 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
26 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
115 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
116 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
310 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
59 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
92 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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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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144 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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2answers
83 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
88 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
62 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
135 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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46 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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104 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
186 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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1answer
60 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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709 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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50 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
73 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
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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
65 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
68 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
99 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
106 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
147 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
36 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
102 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
49 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
88 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
198 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
70 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 ...