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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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Simple transistor switching example should show LED off

UPDATE So even when I remove the switch, the LED is still on (see image below). I.e. there's nothing connected to the base; only to the collector. I'm using the same 2N2222-331 transistor that's in ...
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RGB LEDs with arduino/transistor won't dim

Why doesn't this work? I have fifteen RGB LEDs wired up with this configuration. The transistor I'm using is the MJE3055T. Are the transistor's voltage ratings (collector-base, collector-emitter) ...
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3answers
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Replacing a transistor when I can't find any info on it

I am attempting to repair a Sonix Ultrasonic Cleaner and I have found that the only parts that have gone bad are two power transistors, SIV300004. I emailed Sonix and they want to sell me the whole ...
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How do I make the turn off and turn on time equal in a NPN transistor?

I have a simple NPN switch, see the diagram. I feed a 100KHz square wave (TTL) to the base of this transistor and it turns on very very fast (a few nSec) but it doesn't turn off as fast, it almost ...
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1answer
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In a BJ-Transistor, why do we need to bias the junctions?

I'm new to electronics and I'm kinda confused about transistors. In a bipolar junction transistor, why do we need to forward bias the emitter-base and reverse bias the collector-base?
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How do I know if which leg is the emitter or the collector? (Transistor)

I'm new to electronics and here's a newbie question that I would like to ask: How do I know if which leg is the emitter or the collector in a Transistor (For both PNP and NPN) using only an analog ...
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4answers
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How do I make a real-world verison of this LC circuit?

I'm trying to build the LC oscillator show on the bottom of this page for some school project and I'm having a bit of problems translating the theoretical circuit into a real-world one. Here's the ...
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npn transistor base current question

Hi i am new to using transistors for signal amplification. Can someone explain to me how to figure out the amount of current being drawn into the base of the transistor when it is in the common ...
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Why do you need 2 resistors when hooking up a transistor as a switch

What is the point of R2 in the following diagram: I get that R1 controls the current to the Base, but what does R2 do?
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The 'gap' between understanding of transistors and their application in real circuits

How do they even work? I'm in senior high school year and have electronics as a subject. I'm really interested in getting to understand this and take up electronics in college too. But now this seems ...
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3answers
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SRAM memory cell - what kind of flip-flop

There is a classic 6T SRAM cell (image from wikipedia): It looks like (two inverters in opposite directions and interconnected in and out) and works like some flip-flop. But what kind of flipflop is ...
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Problems with Wien Bridge oscillator circuit simulation in Mutisim

I am trying to build a Wien bridge oscillator that oscillates at 2.1kHz and that can be switched on by a transistor. The reason for me placing a transistor switch in the circuit is so that I can turn ...
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2answers
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Demodulating a signal generated by IR LED/ phototransistor pair

I am driving an IR LED with a 20kHz square-wave signal (I may/ may not use PWM) and I am trying to demodulate the signal being generated by the corresponding phototransistor. I don't have access to ...
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What kind of transistor do I need to amplify an Arduino's PWM outputs?

I'm planning on having 30 incandescent lightbulbs be controlled by my arduino uno on 3 channels (10 bulbs to a channel in parallel). I've used the arduino before to control a number of red, green and ...
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434 views

Converting an analog signal of varying maximum and minimum values to a series of pulses

I have a situation where I need to convert an analog waveform into a series of pulses. The generated signal will be coming from an IR LED/photo-transistor pair that will output a signal whose maximum ...
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3answers
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Determine suitable resistor for the base of transistor as switch (NPN)

I have designed a program to count the frequency and time period of the pulse generated by a 555 timer IC using PC Parallel port. I’ve connected a base of BC547 (NPN) transistor to the output pin (no. ...
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4answers
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Help with TIP122 darlington transistor

i want to use the TIP122 darlington transistor with my atmega8 to control a 3A 12V geared DC motor. i found that the current gain is 1000 for tip122 from its datasheet. so the base current for 3A ...
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The motor gets slower and continues to decrease in speed when using 6+ transistors in the circuit, why does this happen?

Using a simple light circuit to power a motor, when using 5 transistors, the motor spins fast increasing in speed and amps as each transistor is added. However, when I added a 6th transistor, the ...
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2answers
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Not use current limiting resistor for switching device on off using TIP122 possible?

I wanting to control MP3 player and amplifier box through PIC board. My project is doing announcement when person standing in near PIC board with proximity sensor. When proximity sensor detecting ...
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2answers
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High Voltage Series Pass Transistor - Low Voltage Control

I am having some difficulties getting my output stage to work correctly. Here is some info: I have a +48VDC source with a series pass transistor to drive a load between +45V and 0V. The control ...
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1answer
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difference between output resistance, ro, and finite output resistance Ro?

What is the difference between the concept/meaning of output resistance, ro, and finite output resistance Ro in context of a circuit with MOSFETS (ie. a MOS current mirror)? thanks
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1answer
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Transistor or Relay which I will use

I have plan to create a switch ON-ON, this switch will be activated or become ON if there is a supplied current. There is a common (C) connection point to A/B, in initial no current supplied by the ...
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Why are h-parameters used?

What is the reason for using h-parameters when describing transistors? Why are they used instead of the physical description?
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1answer
340 views

Features values of typical BJT/MOS transistors

Is there a page that lists the values of all the features of typical BJT/CMOS transistors? e.g. ON-resistance, gate/base capacitance, amount of power the D-S/C-E junction is able to hold etc. Of ...
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3answers
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Going from Transistors to Gates to…IC's?

So I am trying to understand I guess what is probably a basic concept of computers. I was taking a look at this previous question: From Transistor to Gates And it's accompanying link: http://www.cs....
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613 views

Transistor in saturation mode?

I was wondering why do we so often want out transistor to work in saturation mode? Ie. For a MOS Current Steering Circuit we want our transistors to operate in the saturation region....
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1answer
7k views

MOSFET Turns on without voltage on the gate?

I am using the following transistor to turn a motor on and off: http://pdf1.alldatasheet.com/datasheet-pdf/view/418991/INFINEON/IPP096N03LG.html I am applying 12V to the drain and 0V to the gate... ...
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4answers
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Question about the basic differences between a MOSFET and a FET

I'm still new to all this stuff, but I'm slowly trying to understand. I'm getting most of my information from "Getting Started in Electronics" (Forrest Mimm's book) Okay, so MOSFETs allow current to ...
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1answer
186 views

Transistor terminal impedence?

Can some one explain the concept of transistor terminal impedance? What is it, and why is it important? Any links to useful notes/resources will also be greatly appreciated.
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4answers
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Intrinsic Gain vs. Voltage Gain

I was wondering what the difference is between intrinsic gain and just "normal" voltage gain of a circuit i.e Vout/Vin?
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4answers
2k views

Low power, low voltage, slow (0.1Hz) oscillator?

I had the opportunity to analyze a very interesting circuit today using a programmable unijunction transistor as a timer. The power supply varies, and the circuit must operate on under 10uA of ...
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3answers
350 views

From Transistor to Gates

Does anyone know any links, books, tutorials etc. that will help me better understand how transistors are used to design gates/functions? Here is a link that does a good job of explaining the basics. ...
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6answers
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Replacement for 2N6027

I am working my way through Make: Electronics. For some experiments in this book, you need a 2N6027 programmable unijunction transistor (PUT). The shop I am buying my parts from doesn't have this ...
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When to use what transistor

So there are several types of transistors: BJT JFET MOSFET Combine all that with the various flavors of each (NPN, PNP, enhancement mode, depletion mode, HEXFET, etc) and you've got a wide array of ...
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3answers
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Switching DC with MOSFET: p-Channel or n-Channel; Low Side Load or High Side Load?

I think, it is time I understand working principle of MOSFET transistors... Suppose that; I want to switch voltage on a resistive load by a MOSFET transistor. Any control signal between -500V and +...
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3answers
12k views

Equivalent circuit of a solid state relay

I want to switch 50V AC voltage. Maximum drained current will be 5A. Frequency is 50Hz. Switching speed is not important, can be real slow, it is not a problem in my application. I wanted to use ...
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How can I find a replacement for a transistor?

I have a circuit that uses BC106 and 2N3634, which can't find in store (where I live). Is there any website which could help me find an equivalent transistor? For instance I want to replace BC106 and ...
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How does this transistor work?

The picture shows a detail of schematic diagram of the LM555. I presume the horizontal line is the base, but I'm not sure I understand how the transistor works. What is the effect of connecting base ...
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1answer
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Strange (flyback?) diode in a circuit with a transistor switching an inductor

Edit: The following question is related to a perpetual motion machine, a "Selfrunning Free Energy Muller MotorGenerator powering a 20 Watt bulb" The switching device shown on the circuit was ...
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How is this use of a transistor?

Im working with a LM3915 makeing a vu-meter. I dont think the LM3915 will directly drive more that 1 LED. I'm looking to find a way that I can hook up more that 1 led to the LM3915. I think that ...
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1answer
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What transistor do I need to drive many LEDs and how should I hook it up?

I know that a transistor amplifies a signal, but I've never used one. I have this design here and I want to add 15 LEDs connected to each pin, instead of 1. How I could incorporate a transistor to ...
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1answer
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AC and DC supply from Arduino?

Does the Arduino Uno supply AC or DC power when connected to the computer via USB? Can we specify is we want AC or DC? I am trying to build a circuit that has a transistor but I don't currently ...
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Best way to get +5V or +12V or 0V from arduino pin

I am working on an eeprom programmer as an Arduino shield. There are two pins on my eeprom that require a 12V signal as part of the programming process. One of them is an address pin that I am also ...
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4answers
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Is this a proper use of a PNP transistor?

I'm attempting to use a transistor to switch on and off an SSR, which in turns switches on and off a solenoid. I originally used an NPN transistor (2N222), but this caused problems when the MCU ...
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3answers
6k views

transistor as low-leakage diode

I found this application in AD's OP77 datasheet: Apparently they (ab)use a 2N930 transistor's B-C's junction as a low-leakage diode. Is there any reason why you would choose a transistor over a ...
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2answers
320 views

Finding a Transistor and Other Parts

I consider myself only a novice when it comes to electronics... I can dissect most consumer electronics and figure out how they work; however I am having issues getting over the learning curve when it ...
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2answers
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Totem Pole Output Driver

I was wondering if someone could explain what a totem-pole output driver is? I have seen the term mentioned in connection to the inner circuitry of an AND gate (consisting of transistors) and in ...
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4answers
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Need an XOR gate that works up to 2 to 3 GHz

I have encountered an unusual situation in which I require an XOR gate that will function reliably when presented with a square wave input with a frequency between 2 and 3 GHz. I know that desktop ...
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What kind of resistors do I need to use in this Canon remote switch, if it is possible at all with the P2N2222A transistor I have?

I'm a total electronics n00b set out to create an intervalometer for my Canon EOS 350D camera which seemed super simple from the outset, but I got a bit blocked with creating a switch using a ...
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Why is a MOSFET triggered by Vgs and not Vgd?

Looking carefully at this diagram of one type of MOSFET: (found in this application note) We can see the device is virtually symmetrical. What makes the gate reference itself to the source and not ...