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. T

    What Is the Impedance Between the Base and Ground in a Common Emitter Amplifier?

    Firstly, sorry if this is in the wrong section. I'll happily move it if it should be somewhere else. Homework Statement What is the impedence between the base of the BJT and ground of the common emitter amplifier circuit. Homework Equations Ic = IE The Attempt at a Solution So I...
  2. L

    Site that clearly explains transistors

    Homework Statement friends, i have difficulty in applying KIRCHOFF VOLTAGE LAW in transistors. i am confused because it is totally different from circuits with batteries and resistances where finding the path of closed loop is easy say wheatstone's bridge. but in transistor i cannot...
  3. B

    Transistors: NPN, PNP, which is preferred, how do they work?

    Hello, I am a High School senior that is going to major in EE next year and I am a having some serious trouble with transistors. I understand them at the most rudimentary level (they function like switches, right... please tell me I am right?) but the nuances that come into play when actually...
  4. K

    Lamp, p-n, nanotubes transistors

    I need a professional pure English literature at this field, can you help me via some links?
  5. P

    Need help with my transistors and voltage amplification

    Homework Statement Does the common emitter circuit exhibit voltage amplification? That being said, how would I develop a more accurate transistor model than the first order-model?The Attempt at a Solution I'm not sure what voltage amplification is, though the hint states that amplification is...
  6. Sigurdsson

    Understanding Transistor Voltage Amplification

    Homework Statement I've been reading about transistors now for a while and there is something that doesn't add up. It's about how the collector in a transistor amplifies the output voltage. And then they say... What I was thinking is that when the collector current increases...
  7. U

    Semi conductors(especially transistors).

    Hi everyone, I've been doing semiconductors lately,and believe me,I'm going absolutely nuts over it! This is especially when it comes to transistors. I have worked pretty hard,and I need to clear up some details before I can be confident in this topic. I'll put forward two questions that...
  8. M

    Transistors for 3 Amps Saturation: What are My Options?

    the title says it all... my question is simple... are there transistors easily available that can be configured to provide upto 3ampers in the saturation region? if yes, whch ones?
  9. P

    Conceptualling understanding transistors

    Okay, so my basic understanding of an NP junction (diode) is as follows. When no external voltage is applied, some of the electrons in the N type material jump over to the "holes" in the P type material. The holes then end up moving back into the P type material further, and you end up with...
  10. G

    Understanding the Physics Behind Common Emitter Transistors

    Hello, I would like to ask someone to explain me the basic physics of the common emitter configuration. With the common base configuration i am understanding all the processes with holes and electrons in the npn transistor perfectly. In the common emitter configuration i can`t understand...
  11. K

    Troubleshooting Transistor Circuits: Common Issues and Reliable Testing Methods

    I was using that diode/transistor testing thingy on my multimeter to verify two transistors I accidentally cooked in a circuit. I used some de-soldering wick. To my surprise, both still seem to work, but the circuit does not. What else might go horribly wrong when soldering? And is that a...
  12. I

    Learning H Parameters of Transistors: A Guide to Electronics Books

    can someone recommend me a good electronics book to learn about h parameters of transistors
  13. V

    What Are the Best BJTs for a 17.5 MHz Pulse Input Application?

    Hello everybody, I have an application which needs a pulse input ranging from +15v to -3v operating at 17.5 Mhz. The load capacitor is 150pF and the required rise and fall time of the pulse is 10nS. I am building a circuit with BJT's (both NPN and PNP) . I need some idea about the criteria for...
  14. P

    How to identify different transistors?

    Hello, I bought some large "grab-bags" full of electrical components (I was looking for a good deal). But while trying some of the transistors out, I noticed that they're not all the same. They ALL look like this...
  15. F

    Bipolar transistors and pulse amplification

    hello i have been having trouble working with bipolar transistor. i have been taking pulses that at less then 1us long and amplifying them with transistors. how ever if i have a bipolar transistor as part of my amplifier whether it is my inputs are as part of another stage the pulses always are...
  16. ╔(σ_σ)╝

    Engineering Solving CMOS Sum of Products: 30 vs 28 Transistors

    I'm doing some reading about CMOS circuits and the likes. In the book I'm using it tells me to derive the simplest sum of products for an expression from a truth table. The canonical sum of product is as follows: *- AND !- NOT + - OR (!x1*!x2* !x3*!x4) + ( !x1*x2*!x3*!x4)...
  17. M

    Identifying Unknown Transistors: G9012 & sts9014c

    I have two transistors that I can't find any info on (G9012, sts9014c) how can I determine what type they are?
  18. M

    Connecting Dual Supply Opamps in a Single Supply Circuit with Transistors

    I have a circuit with single supply lm324 and I need to replace them with precision opamps but I can only get dual supply ones. How would I connect the dual supply opamps in the circuit? (the circuit also has PNP and NPN transistors).
  19. D

    Uncovering the On/Off Ratio of Silicon Transistors

    Research-related question: What is the typical on/off ratio of a silicon transistor? This seems like basic information, but I can't find it anywhere. Also, how high does the on/off ration need to be in order for transistors (say, in a logic circuit) to function correctly? Thanks!
  20. B

    Vbe temperature coefficient of transistors

    Something I'm having trouble grasping - if the Vbe temperature coefficient is -2 mv/degree C, why does the collector current INCREASE instead of decrease with increasing temperature? If the temperature rises and the voltage base to emitter drops, wouldn't the smaller Vbe cause less emitter...
  21. X

    How Do Quantum Well Transistors Transport Charge Carriers?

    My understanding of a quantum well transistor is that it is created by sandwiching materials with higher bandgaps with smaller ones, so that it creates a potential well. So for instance, electrons will be forced to be confined within the well, as they would travel along the Quantum Well channel...
  22. A

    Understanding how transistors work

    I am not fully understanding how transistors work. It would be great if someone could explain to me more thoroughly. As I understand it and have read transistors can be used as switches or to amplify voltages. Say then I needed to amplify 5v into 12 volts. How would I do this with a transistor...
  23. T

    Transistors and Diode Test

    Homework Statement Explain why the BC junction will give a smaller voltage drop, and will thus have a higher voltage measured then a BE Junction. Homework Equations N/A The Attempt at a Solution Okay, hopefully this is the right section to post this in. See, I have read the book...
  24. L

    How Is Gain Calculated from Base Current in an NPN Transistor?

    Hey! Does anyone know the equation of gain as a function of base current for an npn transistor? thanks
  25. K

    Field Effect Transistors (fet)

    Hi! I am learning this topic of the electronics and they say that "for an n-channel Junction FET, gate current is to be avoided; consequently the gate-channel junction is never foward biased". My question is why that gate current has to be avoided?
  26. M

    Commanding 2 Transistors with one one command circuit

    Hi to all, I know how to command a transistor, using a comparator with a sinusoidal and a triangular signal as inputs. But let say I have two transistors, T1 and T2. Using the same command, I want that when T1 is ON, so T2 is OFF. vice versa. How can I achieve this? Thanks!
  27. S

    Voltage Drop & RE in NPN Transistors

    Is the voltage drop across the emitter in an NPN transistor equal to 0? What is the purpose of RE (found immediately after the emitter?)
  28. S

    Understanding NPN Transistors: Emitter, Collector, and Capacitor

    Hey guys, was just wondering if you could clear up a fact about NPN transistors. 1. Is this emmiter current slightly larger than the collector current? 2. The reason why the emmiter current is slightly larger is because the emitter current is a combination of the collector current plus the...
  29. H

    Can Mohammed Gaussi help with my high frequency transistor troubles?

    hello every body ; i have a big problem with transistors at high frequency ; their equivalent circuit ,parastic elements,transfer functions; can some body help; or give me alink to a convinent reference that can help. :cry:
  30. P

    Break frequencies for directly coupled transistors

    Homework Statement The problem asks to determine the break frequency at the base of Q2 (which is fine I have no problem with that), but the whole assignment never asks for the break frequency at the COLLECTOR of Q1, then later asks to produce a bode plot of the transfer function. See the image...
  31. B

    Understanding Transistor Switching and Choosing between PNP and NPN Transistors

    Hi all, I hope you guys can help me with my confusions here: 1) I don't understand the usage of transistors as switches. Why would you use transistors as switches, and how does that work?? 2) Why would you choose a PNP over an NPN transistor. I've been reading this book and I don't...
  32. Hans de Vries

    High-k/Metal gate transistors going into production at Intel, IBM and AMD

    After many years of research, micro processors will be build of transistors using different materials as have been the case in the past 40 years: "Gordon Moore, 78, came out of retirement, where he spends some of his time in Hawaii, to issue a statement Friday about the Intel team's...
  33. G

    Transistors: Gaining Insight into the Physics Behind the Magic

    Hi, I'm currently a graduate level physics student taking a course in analog electronics, and I'm really stuck on the idea of transistors. I am reading "the art of electronics", and it's explanation of transistors is horrible, and aside from the fact that i know they "magically" cause a gain in...
  34. G

    How does tunneling explain the behavior of transistors in BJT and FET devices?

    Yup. I've been looking around about it for a while, I delved into electronics books, they mention things like hole/electron flow, energy bands, but I haven't understood how transistors actually work. I've heard that diodes, transistors and other semiconductor materials involve tunneling, so...
  35. ranger

    How do transistors really work?

    I'm looking for a good tutorial that explains how a transistor works. My textbook doesn't do a good job. I searched the internet and found this. But I'm questioning the validity of this document. He really mentions some strange things contradicting what I had previously known. I would be...
  36. I

    Negative power and PNP transistors

    Hello, From what I have learned, when someone refers to negative power, they are referring to a point in a circuit that has lower voltage compared to another area that has more voltage. For example, one test point in a circuit is 8 V while another test point is 4 V. That 4 V point in the...
  37. R

    Project on transistors and how they work

    Hey, I'm doing a project on transistors and i need some help on how they work. So far I know that a transistor can amplify the current of the flow of electricity and contains 3 layers 1 being Silicon. Please, I need additional information on transistors (like an hour worth of info).
  38. C

    Semiconductor P-N Junctions: Transistors or Diodes?

    Is a semiconductor with a p-n junction considered a transistor or just a diode? If it is just a diode, are transistors always triodes?
  39. H

    Transistors and the development of physics

    How is the transistor an important advancement in physics?
  40. C

    Frequency Response of Amplifiers (BJT and FET transistors)

    Hi, I have a question pertianing to the effect of capacitance of BJT amplifier circuits on the low and high frequency response of the amplifier. Why is it that the coupling and the decoupling capacitors, in effect, only affects the low frequency response of the amplifier, and why is it...
  41. M

    Understanding Transistors: A Basic Guide

    How Transistors Works? tks!
  42. N

    Description of bipolar and unipolar transistors

    Hi, Does anyone know any website with description of bipolar and unipolar transistors (analysis of DC U-I characteristic...) Regards, Niko
  43. B

    Quantum Mechanical Transistors

    I was wondering if anybody had any information on Quantum Mechanical Transistors.
  44. Loren Booda

    Transistors vs breast implants

    What is the relationship, if any other than homophony, between silicon and silicone?
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