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. L

    How is this transistor been killed?

    This is a homemade failure and i need to find out how is the transistor damaged after summited to these 3 tests: test 1. base: pump in correct Vbb emitter: grounded collector: open test 2. base: open emitter: open collector: pump in correct...
  2. S

    Transistor cant understand even a bit

    i can't understand the transistor completely i can understand how it works but this stupid conventional current is confusing me completely please can anyone give a lengthy explanation on working of transistor CE CB CC types. i don't understand all these types of transistor i.e how current...
  3. S

    Β on NPN bipolar transistor

    If we make an NPN transistor and change the base doping level so that we get a higher consentration of holes will β increase or decrease? Why? I know β=IC/IB. Will more holes in the base make more electrons pass from the emitter to the collector increasing IC and thereby β? Or will IB...
  4. S

    Need help with confirming if this 555 timer circuit with transistor will work?

    I am an electrical engineer student at SIU and I'm working on an personal project where I am trying to use the following items to supply current between 450-600 mA: 555 timer 2N2222 transistor 4 AA batteries in series for 6V Resistors and capacitors on 555 timer while just resistors on...
  5. U

    Difference between mechanical switch and a transistor switch?

    Doesn't a transistor switch need a mechanical switch? Otherwise, how does the transistor switch turn on and off? Does the switch have a "mind" of it's own?
  6. S

    PNP transistor saturation voltage

    Hi, Anyone here can tell me how to control the saturation voltage of a pnp transistor? I was actually doing a project and my design using a pnp transistor to energize a 5V relay.Since I am using 5V supply,I can't afford to drop too much voltage at VCE of the transistor. The design was...
  7. D

    Can someone explain me transistor as switch

    I want to know about the internal capacitance of transistor cbc and cbe
  8. B

    Find 500 MHz UHF Transistor for Project

    I am trying to find an 500 MHz uhf transistor for a project and I need one which is big enough that i can solder (i.e., not a mm wide) and it has to have the s parameters on the data sheet. If anyone can help me with what i am looking for that would help out a lot! Thanks
  9. S

    Transistor Biasing: Calculating Ic, Ib, and Power Dissipation

    Problem Statement: 1. Given that the beta of a transistor is 36, Vcc=5v, Vbb= 3.6V, Rc=440 ohm, Rb=640 ohm, find Ic, and Ib. Also find power dissipated across transistor. Figure: http://yfrog.com/7hdiagram1j Assume silicon diode. [Ie vbe = 0.7] The attempt at a solution I applied voltage...
  10. R

    European transistor conversions

    I got a electrical wiring diagram from my dads friend for a device that he wants me to build for him but the wiring diagram is from Ukraine and i can not seem to be able to find any of the transistors for the device, If anyone can help it would be great. The numbers are KT835, KT827, and a...
  11. U

    Solve NPN Transistor HW: IB, Ic, V Rc, Vce

    Homework Statement In circuit (figure), there is negligible potential drop between B and E, where β (current gain) is 100, calculate (i) base current (ii) collector current (iii) potential drop across Rc (iv) Vce (Ans: 11.25 µA, 1.125 mA, 1.125 V, 7.875 V)...
  12. A

    How a cascaded common emitter transistor amplifier is modelled

    I want to learn how a cascaded common emitter transistor amplifier is modeled. I also want to know how all the calculations are done with regards to current and voltage gains, input and ouput impedances. I want to also know how we do the calculations with and without the emitter reistor. Can...
  13. A

    5 Methods to use a transistor as Diode.

    Homework Statement List at least five methods by which a transistor can be used as a diode. Homework Equations N/A The Attempt at a Solution I know three configurations viz. Collector Emitter Short, Collector Base short and Base emitter Short.. What would be the remaining two...
  14. K

    Transistor Switch for R2R Ladder DAC Circuit

    hey! friends i have to construct a two-ways switch. Can i use a transistor in that case. i means i am constructing a R2R ladder DAC circuit. in that circuit, there is a switch in two ways- originally ground and connect to ref voltage when switch is on. Please suggest me, which device is the...
  15. H

    Help needed with replacement of burnt out transistor

    does anyone happen to know what resistor i would need for a pair of 850Mah rechargeable batteries as the one in my hair clipper burnt out when i replaced the old rechargeables which were 300Mah cheers
  16. L

    Turn ON Transistor: Requirements & TTL Inverter Circuit

    What is the requirement to turn on a transistor. I always thought Base-Emitter junction should be forward biased. But I was looking at the TTL inverter and in that ckt, the collector of one transistor is connected to base of another transistor. How do you find out the voltage on the collector...
  17. B

    Designing and setting the operating point of a single tuned transistor amp

    Hello everyone, I'm just getting started in studying radio frequency design and have a question about amplifiers with a tuned circuit as the load. When setting the operating point of a standard class A transistor amplifier with a resistive load, one uses the collector resistor to set the...
  18. N

    Is a transistor a switch or an amplifier

    After doing some research, I am still confused is a transistor a switch or an amplifier. If it can be used as a switch how do I find the part that will work with the gate voltage that I give it. mouser.com wasn't really helping me in finding the right part.
  19. K

    Is there a generic transistor model for Capture CIS?

    I have been searching for a generic model of MOSFET/BJT transistors for Capture CIS. I would like something where I can easily edit K, V-Threshold, and B_f (beta-f) without messing with channel lengths and widths and such. Does anyone know where I can download such a thing?
  20. N

    Transistor Approximations: NPN BC548 vs. 2N3904, PNP BC559 vs. 2N3906

    Hello everybody, I'm currently taking Electrical Engineering as senior physics major at Fordham University and have decided to take on a little side project to gain a better understanding. What I'm attempting to create is my own Transistor Logic -> RS-232 (Rs-232 refers to the serial...
  21. A

    Simple transistor problem (emitter follower)

    Homework Statement the question can be found here: http://www.mailfreeonline.com/uploader/04AEED12.jpg i'm having issues with parts (a) and (d). the rest i think I've done correctly, but it would be helpful if someone could verify my answers. Homework Equations The Attempt at a...
  22. T

    Chopper Transistor: Significance & Pulse Generation Explained

    Can anyone explain to me what is the significance of a chopper transistor as opposed to a normal BJT? I read online that its used for square wave pulse generation, but I don't really understand what the mechanism is. Thanks
  23. I

    Help with Secured Wire Loop Circuit - 2N7000/2N3906 Transistor Questions

    Hey guys. Can someone help me with this circuit? http://www.discovercircuits.com/H-Corner/secwireloop.htm Where it says "beeper" do they mean a speaker or do they mean a buzzer? And can I replace the 2N7000 transistor with a 2N3906?
  24. N

    Transistor Action: Understanding Vbe, Vc & Ic

    "Transistor Action" Dear Forum, I have a question about what is often referred to as "transistor action". I understand how a transistor operates within a circuit, and the characteristics of such a circuit, but I would like to learn physically how the bipolar transistor is able to control...
  25. A

    Intrinsic resistance of a transistor

    In my circuits class we were talking about bipolar transistors and our prof. mentioned that every bipolar resistor has an intrinsic emitter resistor. So, I tried modeling a couple of circuits in SPICE to see if I can replace the transistor with another circuit (voltage source, current source...
  26. D

    Simple circuit with a transistor

    Homework Statement Here's a crude description of the problem until my attachment is approved: it's essentially a voltage divided connected to a common-emitter amplifier (I think). There's a +10 V line connected via an 8.4 kOhm resistor to the base of the NPN transistor, and a 1.6 kOhm resistor...
  27. F

    NPN transistor with lowest Vbe?

    Hi - I am looking for an NPN transistor with the lowest Vbe I can get. Any suggestions for specific transistors? (rather than a material class i.e. GaAs) I only have 3.1 volts on the collector and the emitter voltage has to be above 2.5 volts to get a circuit to trip. So 3.1v - 0.7v =...
  28. C

    Question about Walter Brattain’s field-effect transistor principle.

    Question about Walter Brattain’s “field-effect transistor principle”. The Wikipedia says “On 17 November 1947 John Bardeen and Walter Brattain observed that when electrical contacts were applied to a crystal of germanium the output power was larger than the input.“ Can someone please...
  29. E

    Backgate Field Effect Transistor

    Hi At the moment I am trying to make a field effect transistor on a SOI wafer. The plan is to omit the top gate in order to get a backgate configuration. Besides making the transistor I would also like to calculate the IV characteristic of such a devices structure. I am familiar with the...
  30. W

    Transistor radio/kWh problem

    **Transistor radio/kWh problem** A transistor radio operates by means of a 10.0 V battery that supplies it with a 48 mA current. (a) If the cost of the battery is $0.55 and it lasts for 300 h, what is the cost per kWh to operate the radio in this manner? 3.819 dollars/kWh...
  31. E

    How Does a Potential Effect Transistor Work?

    Hi Is there any one, that can explain how a potential effect transistor, PET, works? I would like to know how the current is controlled by changes in the potential. Thanks
  32. G

    Transistor as a zener diode

    Can anyone explain about or point me to any articles about using transistors as zener diodes ? Why not just use zeners, and what connections (c-b short or e-b short) and their pros and cons ?
  33. T

    Transistor hFE equation question

    Homework Statement Showing how to get: Z_{out} = \frac{Z_{in}}{h_F_E + 1} from \Delta I_E = \Delta V_B/R Homework Equations \Delta I_E = \Delta V_B/R Z_{out} = \frac{Z_{in}}{h_F_E + 1} \Delta V_E = \Delta V_B The Attempt at a Solution I am trying to prove...
  34. L

    Transistor darlington pair question

    A bit confused about how it works. Link - http://www.technologystudent.com/elec1/transis2.htm (3rd fig from top) The way I understand, transistor TR1's Base-emitter conducts, which fwd biases B-E junction of TR2. This in turn will turn on the lamp, but it won't be really bright. Once its...
  35. J

    Calculating RoE for AC Equivalent Transistor Amplifiers

    Hey everyone, In my EET program we're going over AC equivalent transistor amplifiers. We've gone over how to do some of them in class but I can't seem to figure out how to find roe. I have the output characteristic of our 2N2222 transistor and made the DC load line but I'm not sure were to go...
  36. M

    Help on understanding NPN transistor

    Hey, I would like help understanding this scenario: (1) base-collector voltage, V_BC, is reverse-biased (2) base-emitter voltage, V_BE, is forward-biased (3) collector current, I_C, is negative Normally, if I_C was positive, I would assume the transistor to be in the forward-active...
  37. J

    Calculate Collector Current w/ Emitter @ 100mA - Transistor Switch

    Homework Statement http://img300.imageshack.us/img300/2640/17569077cy5.jpg The transistor is a N-P-N type. When the siren is functional, the resistance of thermistor is 120 ohm. R1 is 600 ohm. The question is "Calculate the collector current if the emitter current is 100mA". I know that...
  38. A

    BJT transistor Characteristics

    Homework Statement hello guys I have an assignment to "Explain six transistor characteristic curves using the construction and operation of BJTs" I searched all over internet but couldn't find any article relevant.(i found lot of articles about characteristic curves but none of them...
  39. M

    Amplitude modulation using using BC107 transistor

    Homework Statement In my electronics practical class, i assemble a ckt of amplitude modulation using BC107 transistor ,but the modulated wave always has the same phase up and above , there is no phase difference b/w the upper and lower part of the wave . My teacher also couldn't...
  40. S

    Voltage Gain in Midband Region of Transistor Amplifier

    In the midband region the voltage is constant and is assumed to be unity and the transistor amplifier is always used in this region. Doesn’t that mean that there is no voltage gain??
  41. N

    Using transistor to switch leds on/off

    I'm currently using this circuit, but without the rectifying portion,a audio source from mp3 player instead of a mic, and a 4V LED instead of a bulb. My power source is 12v. However, the voltage across the LED is only around 1-1.5V. How can i increase the voltage across the LED? Here is what i...
  42. J

    Calculating base voltage of an npn transistor

    i have been trying to solve this problem for about 14 hours and have gotten nowhere, I am trying to figure out the voltage going into the base of an npn transistor, I am trying to build a circuit where i can take the current from the battery and build a circiut from 7npn transistors in a common...
  43. J

    Transistor Question: Can a Transistor Amplify Current?

    ive been reading about transistors and i have a question i can't find answer to, maybe someone here knows the answer. how much current can a transistor amplify or create? for example, can you push 1 amp of current through the collector of a 15 amp 12 volt NPN transistor and would it boost the...
  44. D

    Can an NPN Transistor Light Up a Bulb?

    Homework Statement circuit diagram showing what has been identified as an NPN transistor with the collector and base connected to neg and emitter conected to pos. The base is also switched by a photodiode and the emitter is supplying a light bulb.Question asks when will the light come on.Can...
  45. S

    Physicsline Exam Q3: Transistor Output - Debating Correct Answer

    The question being referred to is question 3 on page 8: http://www.itute.com/physicsline/phys_trial_exam1_2008v2.pdf Answer referred to is Question 3 Area of Study 2: http://www.itute.com/physicsline/phys_trial_exam1_2008v2sol.pdf I don't understand why they get this answer. The answer I...
  46. S

    Which Components Are Crucial for Biasing an NPN Transistor?

    Is it the voltage divider and/or the Rc resistor that is responsible for biasing an NPN transistor. I am aware the role each play, but was just wondering which part actually biased the transistor, i wouldve thought both?
  47. S

    VCE Physics 2006 Exam Q3: Transistor Questions

    Sorry i couldn't get a copy and paste of the question, but it is as followed on the link: http://www.vcaa.vic.edu.au/vce/studies/physics/pastexams/2006/physics1w06.pdf Question 3 on the electronics section, page 13. I got no ideas how to solve this. I wouldve assumed that there would be...
  48. T

    Characteristics of a transistor

    i have to submit a report on the characteristics of a transistor. there's three zones blockage zone saturation zone and modulation zone i understand the first 2 but the modulation zone i couldn't find out what it is please help if you can thanks
  49. U

    Understanding the Effect of a Capacitor Across Transistor Base & Collector

    Homework Statement What does a capacitor across the base and collector of the transistor do? Apparantly adding a cap (1uF) will slow it down. Can anyone explain how? Homework Equations The Attempt at a Solution
  50. S

    NPN Transistor: Facts, Power Supply, Queisecent Point

    Hey guys, sorry to keep posting things about the NPN transistor but i think I am starting to understand it. I was just wondering if you could confirm these facts for me: 1. An external powersupply is needed to turn the transistor on (by forward-biasing the emitter-base junction), or by using a...
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