What is Transistors: Definition and 144 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. Muhammad Usman

    How EMI is handled in IC fabrication?

    As i recently came to know that the energy is not travelled in the wire infect it is travelled in the space around the wire in the electrical and magnetic field (thanks to varitasium for his video) so my question is particularly related to the IC fabrication. In IC fabrication we have...
  2. E

    NPN transistor overheating even when used with appropriate parameters

    I have been trying to build a simple Current control circuit using a NPN TIP35C transistor but have run into the problem of it constantly over heating and being destroyed. The transistor is the only component that heats up whilst it is on. The supply voltage is 10V, well below the Max and at the...
  3. Quantummanphoton

    Exploring the Possibility of Quarks as Transistors

    Instead of electron transistors why not go smaller particles like quarks?
  4. A

    Can lasers modify the threshold voltage of power-off transistors?

    Hi, I am a phd student in hardware security, I want to know what is the effect of the laser on power-off transistors and can it modify the threshold voltage of these transistors? And is there an equation that links the laser and the threshold voltage degradation? Sincerely
  5. X

    I don't understand transistors in combinations .... Or maybe basics ....

    Hello everybody ! I do have a problem understanding transistor. I know how these solve and work : I know some basics like the voltage on Rb is Vbb - 0,7V. Or something like this. I also Know that the maximal current in this transistor is "defined" by the resistor in the collector which is...
  6. S

    I With chips having 2 nm transistors, are we at the end of Moore's Law?

    AIUI, this is the current level of micro-ization of computer chips. I had always thought that eventually quantum effects start to become an issue when the transistors get to within 20 atoms in distance, which it would seem that 2 nm is.
  7. Y

    Funny observation in matching BJT power transistors

    THIS IS NOT HOMEWORK I design audiophile power amps as hobby. I need to match power transistors. It is A LOT HARDER than I thought. I built a test fixture to hold up to 50 transistors at a time. I try to match sets of 13 to about 1mV which is very tight as Vbe change is about -2mV/deg C. I have...
  8. A

    Need Help Building an Audio Amplifier with D2059 Transistors

    Good morning Thank you very much for being part of this forum. I have a concern. I have 4 D2059 transistors and I want to build an audio amplifier, but I don't have enough knowledge of electronics. And I have one more transistor tip117. Can anyone help me by sending a simple circuit diagram how...
  9. Mr_Allod

    Calculating the speed of a JFET

    Hello there, I believe here I need to find the capacitance of the junction between the P-doped gate and N-channel. Then I could find the RC time constant although I am not sure if there's something more I need to find the speed of the JFET? What I'm unsure of is the depletion width h to use...
  10. M

    How to understand power stage circuits with transistors (undergrad level)?

    Hi, When I look at some circuits, I often get overwhelmed when there are transistors and diodes and I have no idea how to make much sense of it at a detailed level. For example, in this power stage B amplifier, what is the point of the resistors ## R_1 ## and ## R_2 ## in the circuit...
  11. C

    RF Transistors, is there a 'minimum' frequency where they work?

    Some RF transistors are not 'characterised' for lower frequencies, can they still be used? I get that a lower operating frequency (HF/1.8MHz) may not be the commercial target for an UHF transistor (>136MHz) so no effort spent on characterising them. Likewise HF transistors >1.8MHz not...
  12. kolleamm

    Need Heavy Duty Transistors for Controlling Larger Motors with PWM?

    I want to control the speed of a larger sized motor (roughly 8" x 4" x 4", 48v, 5.8A, 30A max ) using a transistor and PWM. The only problem is I can't find any transistors that have enough resistance to prevent the current from passing directly through. I purchased some mofset transistors...
  13. A

    Mosfet, Mesfet vs Bipolar transistors in RF circuits

    I was wondering in general what types of semiconductors are used in most solid state RF power amplifiers like the ones at cell base stations and elsewhere. Do they use mosfets etc which can only switch a square waveform or are bipolar ones also used that can output sinusoidal outputs that can be...
  14. F

    MOSFET Transistors as Switches

    I’ve attached two images from my textbook. One describing how MOSFEET’s act like small resistances when in the triode region and open circuits when in the cutoff region, the other a list of equations describing the behavior of an NMOS transistor. I’m having trouble making sense of these two...
  15. Z

    What are the limitations of using real transistors to build an ideal op-amp?

    What are the transistor characteristics and limitations from building an ideal op-amp?
  16. Boltzman Oscillation

    Engineering How should an H bridge circuit be analyzed?

    If I am given an H bridge circuit such as that below: How would I go on analyzing it? I would personally replace all of the transistors by their circuit models but then what would I do with the motor? Do I replace the motor with it's load resistance or is there more to it? I guess motors are...
  17. J

    Thermal radiation in CMOS transistors

    Inside a CPU, when applying voltage to the gates of the CMOS transistor(high input), are the gate ore another components of a transistor will generate thermal radiation which will be absorbed by the neighboring transistor?
  18. J

    How does this have 24 transistors?

    Our professor is teaching this circuit and she mentioned there are 24 transistors. But I counted and it comes out to be 22 T1 to T4 needs 2 (transistor) * 4 = 8 transistors Each inverter needs 2 transistors. so 7 inverters need 14 transistors. total 22 transistors. Unless we're also creating a...
  19. F

    Do transistors only work with DC and not with AC?

    Hello, I was reading an electronics book which state that transistors work with DC signals only (not AC), suggesting that relays are needed to switch AC signals. Is that a mistake? When used for amplification, I have seen transistors amplifying time-varying signals (which means AC). Unless...
  20. Zeynel

    I Transistors and Quantum Physics

    My question is: What is the contribution of Quantum Physics to the discovery, of the transistor? In Adam Becker's book What is real? I read that, "the discovery of quantum physics in the early twentieth century led directly to the [discovery] of silicon transistors..." He implies that, the...
  21. akaliuseheal

    Use of transistors to turn on an LED

    Homework Statement Hello, I have got input from comparator op amp which gives HIGH or LOW. Based upon that, one of two LEDs needs to light up. Two LEDs should't be ON at the same time. Calculations are not needed, only the schematics. Homework Equations None The Attempt at a Solution I am not...
  22. 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...
  23. 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...
  24. 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...
  25. math4everyone

    Question about Probability of operating time of transistors (MTBF)

    Homework Statement Homework Equations $$f_X(x)=\lambda e^{-\lambda x}$$ $$F_X(x) = 1-e^{-\lambda x}$$ $$\mu = \frac{1}{\lambda}$$ The Attempt at a Solution a) $$f_{X,Y}(x,y) = f_X(x)f_Y(y) = \frac{1}{800} e^{-\frac{1}{800}x} \frac{1}{1000}e^{-\frac{1}{1000}y}$$...
  26. N

    Transistors: Tiny Silicon Crystals, Memory Cells, & Shrinking Bits

    Transistors are tiny crystal of silicon. Transistor switch and it's support component are memory cell. A single memory chip can hold up to 4 transistor ? What is the shrinking bit ? Can you please explain?
  27. 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...
  28. G

    How transistors amplify AC signals

    How are transistors able to amplify full AC signals? What I mean is that a transistor will conduct only if the base emitter junction is forward biased and when you apply high enough treshold voltage to turn it on. Like 0,6v. Then looking at the graph above, from 0 to 120 and from 120 to 0v the...
  29. wolram

    Is Sequential Deposition the Key to Flexible and Wearable Electronics?

    https://www.sciencedaily.com/releases/2016/04/160407150617.htm Just wondering if this will be the next step in electronics, ie, wearable devices and printing electronics. Now, University of Pennsylvania engineers have shown a new approach for making these devices: sequentially depositing their...
  30. EinsteinKreuz

    Hardware Random Generators: Transistors vs Diodes

    So which method works better for random number generation(in terms of flatter frequency spectrum): transistor breakdown or Zener noise? I want to know whether to use a Zener diode or a Transistor when building a white noise generator. And FTR I intend to use Germanium because of its higher...
  31. Y

    Classical How can I better understand transistors and their various uses?

    I am having troubles understanding the working of a bipolar junction transistor(and also its uses as switch, amplifier, oscillator etc.). Can anyone recommend any good book or video explaining it?
  32. C

    Do transistors *only* work with small current in base?

    Quick basic question on how transistors work. Do they only work when a small current goes through the base, or would they function the same with a large current as well?
  33. A

    Problems building a 1 bit / 2 to 1 Multiplexer

    First let me just I'm a total newbie to electronics, but I would like to progressively learn how computers work by building the little components with the small parts, and then work up to the ICs once I understand how to make rudimentary versions. I'm trying to make a 1-bit multiplexer out of...
  34. F

    Amplifiers, transistors and opamps

    Hello Forum, I have recently learned about transistors and their ability to control (amplify) other signals. BJT transistors amplify current. There are also FET transistors. Some devices are termed current-controlled and others are called voltage controlled. Are there amplifiers that amplify...
  35. DocKiru

    What type of transistor works with a 2.7v max source for a DC to AC inverter?

    hello dose anyone know of any type of transistor that would work with a 2.7v max source? I am trying to make a 2v-18v DC to AC inverter. I was using 2 Mosfet transistors with a 60hz oscillator, but the problem was it was barely turning the transistors on and over all not efficient at all. The...
  36. J

    Transistors and current direction

    Can current go either direction in a bjt, mosfet, and jfet? Or are they all usually just one direction? (Especially the jfet. Given the symmetry, I don't see what the difference is between drain and source) Thanks
  37. B

    Suggest one way of sizing the transistors of the logic

    Homework Statement Suggest one way of sizing the transistors of the logic circuit such that its worst case tpHL equals the tpHL of an inverter with a sizing of (W/L)min. Homework Equations I think the only equation is the (W/L) itself. The Attempt at a Solution I have actually done the front...
  38. A

    Field effect transistors question

    [ Mod note: moved from Elec Eng, might have better luck here] I have some basic knowledge of how FET work. But i have a question that i can't see the answer. For example: In a MOSFET we have a p-doped Silicon substrate. Then we have two n-doped silicons, with a oxide layer above the the...
  39. J

    Whats the point of transistors?

    Since you can make all the logic gates with diodes instead, what is the point of transistors considering they take more semiconductor material to construct? Thanks
  40. N

    How programming interacts with transistors

    Forgive the broadness of the question. I know this is a huge concept which entire books have been written about. I am an amateur computer programmer entering my first object-oriented class soon and want to get some things out of the way. When I write lines of code how does the computer know what...
  41. V

    PN Junctions vs Transistors When Building Logic Gates

    Is there any reason why logic gates are built using transistors instead of PN junctions? Wouldn't it be more cost-efficient to use PN junctions? I am referring to CMOS logic gates. Also, what can a transistor do that a PN junction can't?
  42. EngUOL

    Confused About Transistors: Pi Hybrid & Small Signal Equivalents

    Hi everyone. I am starting to study transisors at Uni. and I am confuse in some main concepts. i thought about posting it here so someone can help me up. are pi hybrid signals equivalent circuits used with the same porposes as small signals equivalent circuits? or are pi hybrid signals, small...
  43. M

    Transistors emitter collector flow

    Hello :-) I can't seem to get a good understanding about a part of transistors and how they act. What I think I know about transistors now is as follows: They're made up of npn or pnp called emitter, base and collector, and the junctions between them are emitter base junction and collector...
  44. I

    Designing a +10V Supply with Emitter Follower Circuit: A Practical Approach

    Homework Statement Design a +10V supply with the following specs: Iout =0-100 mA Vout =10V Vin=20-25V (unregulated supply w/ ripple) The circuit will have the diagram attached. The book I am using is The Art of Electronics, which is very "practical" the authoppr says things like why worry...
  45. I

    Designing a +10V Supply with Transistors: A Practical Approach

    Homework Statement Design a +10V supply with the following specs: Iout =0-100 mA Vout =10V Vin=20-25V (unregulated supply w/ ripple) The circuit will have the diagram attached. The book I am using is The Art of Electronics, which is very "practical" the author says things like why worry about...
  46. C

    PNP versus NPN bipolar transistors

    Hi, Could anybody explain me why the base current of a pnp is higher than a npn for the same collector current? Regards, David
  47. J

    Transistors & Conventional Current

    Hi, please could someone help me with NPN transistors. I found this veritasium video on YouTube () and do not think it is correct. He shows a diagram towards the end of the video with a source and drain which I looked up and source is collector and drain is emitter. He clearly shows electrons...
  48. B

    How are transistors and QM tied

    I know that transistors work using QM, but I don't know how, can someone explain this to me?
  49. P

    Explaining the Role of Transistors in Burglar Alarms

    I don't understand what exactly a transistor does in a burglar alarm. I read somewhere that this is its application as a switch but isn't it the LDR which works like that in this particular circuit? It would be really helpful if someone could explain the working in detail, I can't seem to find...
  50. E

    H and y parameters for CB and CE transistors

    Homework Statement When I measure CB ciruit: I have got these results: And here CE: Homework Equations The Attempt at a Solution So.. here is table, how to calculate h parameters: But I don't understand, am I using it correctly. When I use results of my table...