What is Transistor: Definition and 508 Discussions

A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. Transistors are one of the basic building blocks of modern electronics. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.
Austro-Hungarian physicist Julius Edgar Lilienfeld proposed the concept of a field-effect transistor in 1926, but it was not possible to actually construct a working device at that time. The first working device to be built was a point-contact transistor invented in 1947 by American physicists John Bardeen and Walter Brattain while working under William Shockley at Bell Labs. The three shared the 1956 Nobel Prize in Physics for their achievement. The most widely used type of transistor is the metal–oxide–semiconductor field-effect transistor (MOSFET), which was invented by Mohamed Atalla and Dawon Kahng at Bell Labs in 1959. Transistors revolutionized the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, among other things.
Most transistors are made from very pure silicon, and some from germanium, but certain other semiconductor materials are sometimes used. A transistor may have only one kind of charge carrier, in a field-effect transistor, or may have two kinds of charge carriers in bipolar junction transistor devices. Compared with the vacuum tube, transistors are generally smaller and require less power to operate. Certain vacuum tubes have advantages over transistors at very high operating frequencies or high operating voltages. Many types of transistors are made to standardized specifications by multiple manufacturers.

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  1. J

    Power dissipated across a transistor regulator

    Homework Statement [/B]Homework Equations For the 1st part Ohms law and resistance across zener is 10V[/B] I can't get 2nd The Attempt at a Solution For 1st part I took Vi/p = 18V[/B] Putting KVL for left loop of source-->collector-->base-->zener-->ground 18 = Vcb + 10 So Vcb = 8V And Vbe =...
  2. OldWorldBlues

    Trouble understanding common-emitter amplifiers

    Hi there! I've been tinkering with some homemade speakers, and wanted to make a simple amplifier circuit to step up the some 3 volts that comes out of an aux jack to 9 or 10 volts. I decided that the common-emitter model looked the easiest to understand. I was mistaken. This is the simplest...
  3. C

    Looking for the right MOSFET transistor

    I need a MOSFET transistor that will turn off anywhere between 2.5-2.7V and stay on when above that voltage, looking through the datasheets of these transistors, what spec should I be looking for? Here are some I've found that I think may work...
  4. S

    Straight line plot of bipolar transistor - temperature?

    Hey everyone, I'm trying to plot a straight line for a bipolar junction transistor to find the room temperature, T, using my experimental results for the associated base-emitter voltage, ##{V}_{BE}## and collector current, ##I_C##. Here's the equation that I'm using: $$ I_C = α_F {I}_{EO}...
  5. M

    What is a Superegenerative Detector and How Does it Work?

    helo can somebody tell me how does work this circuits please, calculations and the rest
  6. M

    Question about circuits with transistors (current, voltage)

    Homework Statement 1. In Figure A-1 of Experiment 18, assume that Vdc = 8Volts, R1 = 1kOhms, R3 = 7kOhms and there is no R2 resistor. Determine the current in R1 when the transistor is fully on and carrying current. Express your answer in mA. 2. In the circuit of Figure A-1, Experiment 18...
  7. Wrichik Basu

    B What is the utility of grounding in this Transistor case?

    I am attending an online lecture course on semiconductor physics. While explaining the common emitter mode of transistors, the professor sketched this diagram on the board: (I added something more to explain better) I understand that the emitter has to be at the same potential, and that is...
  8. Cocoleia

    Calculating R with Beta in a Circuit

    Homework Statement I have this circuit Where I have to find R given that I=2mA, and Beta =200 Homework Equations Ic=Beta Ib Ie = Ic+Ib The Attempt at a Solution I would have thought that the voltage Vb would be -9.3V, since we have Vbe = 0.7 and at the bottom we are given -10V. Then I would...
  9. G

    Understanding single transistor oscillator

    I see this circuit has many applications for creating high voltage from a battery source in a very simple and compact manner. However, I’m not sure of the exact basis of oscillation - is it: 1. Current flows through FB, turns on transistor. 2. Primary induces opposing voltage in FB due to...
  10. Z

    What Happens to Amplifier Gain When Connecting a Load?

    Hi Guys can you tell me, what will happen to the gain of the amplifier when a load is connected to the output terminals ?
  11. Pushoam

    Measuring the output from a Transistor Amplifier

    Homework Statement I understand that the DC current will not flow through the capacitor once the capacitor gets fully charged. So, after a long time , only AC component of the net current flow through the capacitor. How to show that all of the carying voltage appear across the capacitor...
  12. Pushoam

    Voltage amplification done by a transistor amplifier

    Homework Statement Homework EquationsThe Attempt at a Solution The equivalent circuit is drawn below. It is assumed that the potential drop across the pn junction in forward bias is 0 V(I can't take it 0.7 V as the input voltage is 0.5 V). In this case the p-n junction is equivalent to a...
  13. Pushoam

    Exploring the Role of Charge Injection in the Operation of an NPN Transistor

    In a transistor, the base-emitter junction is forward biased while the base-collector junction is reverse biased. The emitter emits charge carriers.These charge carriers go to the base. My question is: why don't all of these charges flow as base current since this junction provides low...
  14. V

    B Understanding Input Signals in Transistors

    Hello , This doubt arose while studying chapter on semiconductor devices in grade 12 of high school physics . Please clear a doubt in as simple language as possible . In order to be specific with my question I need a diagram which is exactly as mentioned in the video below . Kindly see Note...
  15. Rx7man

    How to choose transistor types

    I'm working on a few little 12VDC projects, and am wondering on the logic for choosing different types of transistors... Bipolar vs IGBT vs Mosfet... What makes one of them a clear choice in each application? I can see bipolar transistors would be ideally suited for for analog/linear...
  16. D

    Engineering Simple DC Circuit Analysis with Transistor

    Homework Statement Homework Equations The Attempt at a Solution All loops are clockwise; KVL Loop around 1V, 120kOhm and VBE (I1 is assigned to the loop): -1V + 120kOhm * I1 + VBE = 0 I1 = IB = 0.3V / 120kOhm = 2.5 * 10-6 A; Loop around 10kOhm, vCE (I2 is assigned to the loop); KVL...
  17. H

    Increase the maximum voltage rating of semiconducter

    Hello, I was wondering if there is any way of increasing a transistor or thyristor maximum voltage ratting in DC? Thanks. Edit: Just to be more precise, I am referring to the off state. I know you can the on state via a resistor.
  18. D

    Find output current of NMOS transistor

    Homework Statement Vtn = 0.4V W/L = 10 NMOS1 Saturation Region Drain = 2.5V Gate = 1.9V Source = 0V Vtn = 0.4V W/L = 10 NMOS2 Triode/Linear/Ohmic Region Drain = 0.5V Gate = 2.2V Source = -2.3V tox = 9um un = 250cm^2/V W/L = 10 Homework Equations Saturation: Id = Kn * (Vgs-Vt)^2/2...
  19. D

    Operation mode of NMOS transistor, can someone check my work

    Homework Statement Vtn = 0.4V NMOS1 Drain = 2.5V Gate = 1.9V Source = 0V NMOS2 Drain = 0.5V Gate = 2.2V Source = -2.3V NMOS3 Drain = 0.5V Gate = 0.9V Source = -2.5V Homework EquationsThe Attempt at a Solution NMOS1 Vgs = Vg - Vs = 1.9V Vgd = Vg - Vd = -0.6V Vgd < Vtn and Vgs > Vtn...
  20. V

    PNP Transistor voltage calculation

    For the B) part, I don't get why is it that for calculating voltage between collector an the emitter (Vce) I take into account diode on base (0.7V), whereas for part A) it's ignored? Why is Vce in part A and part B are calculated differently? Why is it that in part A voltage of 0.7V isn't taken...
  21. Cocoleia

    BJT and MOSFET complete analysis

    Homework Statement I have been given the world's longest transistor problem as an assignment :wink: Here is the circuit: I am asked to find: a) V1, V2 and V3 using DC analysis b) AC equivalent circuit c) AC tension gain: Ava=Vx/Vsig d) AC tension gain: Avb=Vo/Vx e) Total AC tension gain...
  22. T

    What thyristor, triac, diode, transistor for an amateur?

    Beginner here. Learning about electronics. I would like to play with a thyristor, triac, diode, transistor, diode bridge, etc. using 1,5-9V batteries, wires, multimeter. I am buying a breadboard too. What kind of these you recommend for that purpose? There is a wide variety on the shelves please...
  23. Planobilly

    Need some help with a transistor switching circuit

    Hi, The issue: The "more drive" circuit is not working on this Fender Hot Rod Deluxe amp. There is a push button switch that selects the drive channel which is working and the yellow LED comes on. There is another push button call "more drive" which increases the gain to the drive channel by...
  24. ThinkerCorny

    In bipolar transistor, what's the real reason for base to become narrow?

    I'm kind of new in this. Now, I'm especially talking about npn common emmiter configuration. I've read somewhere that base is made narrower to stop the recombination of minority charge with holes in base. And I assume that if base would broad then electron combine with holes creating strong...
  25. K

    Calculating the amplification of a transistor

    Homework Statement In the circuit shown below, I have to find the amplification for when the commutator which connects to the 4 kΩ resistance is open, respectively closed. We know the Beta factor to be 200, and the current through the base is negligible. The transistor is made of silicone...
  26. srinaath

    Electrical DIY wireless power transfer device concept

    i am planning to do a small diy wireless power transfer device. The circuit of the transmitter is receiver has just the coil and load arrangement. my query is, (please correct me if am wrong) -->to induce a voltage in the secondary coil, there must be a varying magnetic field right? -->but...
  27. nothing909

    Calculating resistor values for transistor

    << Mentor Note -- Two threads merged into one >> As a project I have to design a switching circuit for a switched reluctance motor. I've picked all the components I need and I've tried to design the circuit. Open collector - 74LS06N Optocoupler - TLP 251 IGBT - stgp6nc60hd Does the circuit...
  28. F

    Engineering Transistor circuit low-frequency response

    Homework Statement This problem is adapted from the book "Transistor Circuit Techniques" by G. J. Ritchie. Given the following circuit: (1) Calculate the AC gain of the circuit, for frequencies where C1 and C2 can be considered as short-circuits. (2) Sketch the low-frequency response due...
  29. Planobilly

    A general transistor switching circuit question

    Hi guys, I need to design a transistor switching circuit to switch two channels on a tube/valve amp without adding noise or altering the sound of the tube channels. What issues am I likely to have to deal with? Thanks, Billy
  30. adamaero

    Easy transistor question: NPN--the corresponding change?

    Homework Statement Given: an npn transistor having VBE = 0.76V for a collector current of 10mA at T=350 K (n=1) Find the corresponding collector current for VBE = 0.70V 2. Relevant questions a) Wouldn't that temperature be way to high for the transistor to act normally?? I mean 350K is 170F...
  31. seemasdawange

    Improving Transistor Switching for High Voltage Protection Circuits

    Hello friends I'm new here and want some answers from u. please help me to sort out the problem related to my circuit of high voltage protection. in this circuit i regulate the dc voltage using zener diode and then output of zener is given to the base of npn transistor. please check the circuit...
  32. Mathamans

    Is a mazer essentially a transistor for radiation?

    I come to this conclusion because a mazer amplifies radiation; a transistor amplifies electricity.
  33. G

    How is the circuit above biased for temperature stabilization?

    I have a few questions about the circuit above. 1.This is an ordinary CE amplifier, which uses current mirror to provide temperature stabilization and bias for Q2, right? 2. Like Collector feedback bias and Voltage divider bias, this is just another way of biasing a transistor to provides...
  34. thegreengineer

    BJT transistor analysis: common emitter confusion

    Recently I started studying semiconductors and analogue electronics. First I studied the diode and its I-V characteristics and analysis in DC circuits, as well as in AC circuits. Now I started with BJT transistors. I was explained that transistors act as electronic switches. My problem is not...
  35. M

    MIL-STD-750-3 Transistor Testing

    I just want to check my sanity... I am going to be testing some transistors in a lab very soon per the above mil std. The test methods range from Vce, Vbe, hfe and the breakdown voltages that are listed on the datasheet. The transistor at this point is irrelevant. Here's what I need to...
  36. G

    Help with transistor datasheet

    On this datasheet of PN2222A bipolar transistor it is said that Vcesat at Ic/Ib=10 is about 0,3volts. However in the Icollector vs Vcesat graph for the same transistor that I will be posting immediately after I post this thread cause I can't add one more image here, it is shown that Vce hardly...
  37. H

    Engineering Calculate R3 in Transistor Circuit

    Homework Statement Hello, guys! I just wanted to make sure I do this right. Homework Equations Forget about the rest of the circuit and focus only on Q2 and Q4. How to calculate R3? The Attempt at a Solution The way I do it: R3 is basicaly the emitter resistance which purpose is to regulate...
  38. G

    Help with NPN Transistor: VBE, VE, VB

    Hey. I can't understand something. It's about NPN transistor. If it's given a constant base voltage VB, emitter voltage VE and base emitter voltage VBE, then VB = VBE +VE. I can't understand why phisicaly an increase in VE while VB is const will cause a decrease in VBE. Can VBE even be reduced...
  39. LalaDeil

    I'm looking for this transistor

    Hi, I need this transistor, but I have no more references than this number. https://scontent-yyz1-1.xx.fbcdn.net/v/t1.0-9/13886417_1422976724395700_8867555117386392787_n.jpg?oh=cb0057241b92e5fa390e134efba217c0&oe=581E9C28
  40. Sherldonnnn

    Transistor questions in control a stepper motor

    Hello, I am Sherldonnnn. I'm very happy I can ask my questions here to get your help. If you can help me solving my questions that will be very nice. Now I am trying to control a stepper motor with a simple transistor-based switch. I still with to consult with the experts here on some basic...
  41. 1rel

    NPN BJT transistor: base voltage / emitter current

    I don't know how to calculate the voltages at the bases of every transistor shown in the lower row of that picture (~3V (2.9..V), ~2V, ~1.8V). Any help would be appreciated! - I'm currently trying to figure that out... The other thing I don't really understand: Why do the transistors in the...
  42. wolram

    Exceeding Limits: The 621 Million Transistor Chip

    I thought we were on the limit for transistor density but this chip looks like it is way over that limit. From science daily. https://www.sciencedaily.com/releases/2016/06/160617215802.htm A microchip containing 1,000 independent programmable processors has been designed. The energy-efficient...
  43. DS2016

    Pnp transistor with base connected to collector

    Hello all, I have a problem to understand a pnp transistor with base (B) connected to collector (C). When I set the VE (voltage of emitter) at 0 V and the VB, which is the voltage of base and collector nodes, since they are tied together), decrease from 0 V to -1.0 V,the simulation result shows...
  44. H

    What is the expected resistance of a transistor in cutoff mode?

    Homework Statement Hi! I learned how to work with transistors a long time ago. However, it is good to fortify youre knowledge. I was checking a circuit board for issues and found a npn bjt, which Colector-emitter resistance while in cutoff mode, is arround 1k ohms. So my knowledge of bjt's says...
  45. GRASBOCK

    Capacitive touchscreen control using a transistor

    Hello, I'm posting the first time on this forum. I want to create a robot controlled by an Arduino which is able to make a touch signal without using a mechanic arm or finger ( here is a robot with the same goal but using an arm video). I want to take the electrical approach. A modern...
  46. Adrian Collings

    Why is my transistor overheating?

    Okay so I am having this problem with a transistor overheating in a motor control circuit and I am not exactly sure why it is overheating. There is a PWM signal being used to power the transistor from an MSP430 microcontroller. I am using a standard 1N004 kickback diode for the motor and an...
  47. C

    Transistor Logic Gate : NOT Gate Explanation?

    Hi everyone. I would like to ask about this light sensor using not gate circuit. I use LDR as an input and a LED as an output. I have tried this circuit in Proteus, and it works. When the LDR 'off', LED turns on, and vice versa. But i don't really understand about the working principle of this...
  48. T

    Transistor current gain in saturation mode

    Hi, I want to operate my transistor as a switch. I am using this one Datasheet: http://www.farnell.com/datasheets/1868820.pdf In the data sheet, it says the DC current gain hfe = 110 which I am assuming that's for the linear operating region ?, so if my hfe is less than 110 then will it be in...
  49. davidbenari

    Engineering Solving simple transistor circuit

    Homework Statement https://drive.google.com/file/d/0Byf8Tfw7vme8N1ZZaUFzOWQtb0k/view?usp=sharing Determine IEQ ICQ IBQ My problem is that this circuit is overdetermined and cannot be solved. (See below) Homework Equations ##\beta = 75## ##I_E=76 I_B ## The Attempt at a Solution The...
  50. P

    Number of electrons making it through an NPN transistor

    Homework Statement Suppose ##n## electrons attempt to move through an ##NPN## transistor, there's a probability that some of the electrons traversing the ##P## area will recombine and and not make it to the other side. The infinitesimal probability in a region dx is given by...
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