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. E

    Transistor radio amplifier noise in the 70s

    In the 1970s, did transistor radios have RF receive sensitivities down to the 1 microvolt level? If not, what is the highest microvolt it could resolve? But how could it do that? Even modern amplifiers have much noises. For example, at 100kHz, and a very quiet circuit with total noise of...
  2. A

    Bidirectional current switching with single type transistor

    So here is my dilemma. I have a test setup with multiple coils all lined up in parallel in such a way that one end of each coil is connected together while the other is connected to a switch (mosfet) the switches then connect each coil to ground but that ground can become + based on which coil...
  3. 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...
  4. M

    Silvaco: "simulator has unexpectedly exited with status -1073741819"

    Hello, I am simulating the process of NMOS construction. as you know, in order to make the LDD, we need two implantations, one before creating oxide spacer and another after creating oxide spacer. at the last implantation, I am facing an error which is shown in the following image: I put...
  5. O

    I How Small Can a Transistor Be and Still Work Reliably?

    If this is not the correct forum, perhaps someone would be so kind as to move it to a more appropriate one? Thanks. The current trend in computer chip manufacturing is towards making transistors smaller and smaller, so more and more can be packed in a single chip. This has a number of...
  6. D

    Engineering Solve BJT Transistor Q Point Using Thevenin Theorem

    Hello, I need help with this bjt transistor and finding the Q point. The problem I have is that I don't know how to do the thevenin theorem on this one. If someone could help me and show me how its done that would be great. Thank you! The transistor looks like this on the picture: This is my...
  7. altruan23

    Engineering Constant current source transistor circuit - differences between 2 types?

    So basically we can have a constant current but i don't understand this circuit. for example: i can have the Ia what ever I want with current divider rule: Ia = Iq * R2/R3. So Ia is proportional to the ratio of R2/R3. And if i give a resistor at the collector terminal, if i change it between...
  8. altruan23

    BJT emitter circuit weird equations?

    Summary:: So apparently the equations schould be correct but I am not sure about it. Isnt R1 = Ub(10V) - Base voltage / Iq + Ib --> Ub is the source voltage 10V. And schouldnt R2 be :base voltage / Iq?
  9. Raihan amin

    Understanding a heat sensor circuit?

    What I understand is that the β parameter of the npn transistor is temperature dependent. Increasing the temperature increases the collector current and hence the LED turns ON. But I don't understand the resistor arrangement.Also I can see that the diode is keeping the Base-Emitter junction in...
  10. R

    Does Drain Current Increase if Doping Increases?

    I'm an EE with only a surface knowledge of solid state. I know this forum is mostly for students but I don't know where else to find a lot of physicists. Also, please forgive me if this is a dumb question. For a circuit I want to build, I need a transistor that can conduct > 10,000 A, but does...
  11. Mr su

    Can this comparator accept negative voltage as its negative supply?

    I check the datasheet of LM 319 high speed comparator online. I was wondering if LM 319 can accept negative supply voltage(-10V) and its possible to produce a 10V to -10V square wave which oscillates along origin rather than just 10V to 0v as shown below.
  12. D

    Engineering What is the significance of a -4V gate potential in FET-transistors?

    Hi, not really a homework question just a quick question regarding FET-transistor. If the gate potential is -4V does that mean that in the figure below that uGS is -4V. If not, what does it mean and how do you use it in a bigger circuit problem?
  13. patric44

    Changing a schematic diagram to British Standards (BS 3939)

    hi guys i need help changing the schematic diagram of this circuit to British Standards (BS 3939) i know that resistors are represented by boxes, but not sure about the transistors or Vcc and GND.
  14. doggy

    Understanding a Single Transistor Flyback Transformer Driver?

    I've been watching a few analyses of CRT flyback transformer drivers and can't understand why the transistor would shut off. To my naive perspective, it appears that the transistor should never shut off due to the positive DC voltage applied constantly to the base. I'm aware that this isn't the...
  15. doggy

    Electronics NPN transistor is always flickering and on

    I'm completely new in hobby electronics, and I assembled the following circuit to control a power LED over wifi using esp8266. The problem is, that it is always, on and sometimes flicker , no matter,what I send via GPIO1 port. I know that this is not an esp8266 problem, I tested my program with...
  16. Stonestreecty

    Troubleshooting Laser Diode Circuit with Arduino and PN2222a Transistor

    Hi, all I have a circuit where the base transistor (PN2222a) leg is plugged into the pin 9 of the Arduino. When I power everything up and send the signal from the Arduino to the transistor base leg, the laser diode doesn’t light up, but my design strictly follows Complete Tech Guide to Laser...
  17. M

    Transistor base voltage calculation

    Hello, I am trying to find base voltage. In attached picture (using Multisim) there are two separate circuits. Here is how I am doing the voltage divider: Circuit on right: Vb = (Vcc - .7)*R6/(R6 + R5) = 3.2V which matches Multisim result. No problem here. Circuit on left: Vb = (Vcc -...
  18. Boltzman Oscillation

    Are ISFETS available for cheap or am I out of luck

    I was looking into measuring the ph levels of a lake nearby where I live. I wanted to tie the experiment to my electronics coursework so I did some reasearch and found the wonder electronic that is the ISFET. Unfortunately, I cannot find anywhere to buy an ISFET transistor; I can easily find...
  19. paulmdrdo

    Transformer Coupled Class A amplifier Single supply

    How can Vce vary from 0 to 2Vcc? In class, I learned that it was due to Lenz Law working in the transformer and a voltage of Vcc being induced to reverse the change in Ic. However, I cannot picture this. Can someone please explain with a diagram of how this comes about in the transformer windings.
  20. Z

    Circuit design question -- 100% transistor functionality needed?

    A question for folks designing circuits, is it the case that 100% of transistors must be functional for the circuit to operate, or are a few transistors allowed to fail in the design, but compensation circuits or redundancy is put in place to prevent circut funtionality to degrade? I'm wondering...
  21. K

    What Factors Determine the Selection of a High-Voltage NPN Transistor?

    Say you want to choose a npn transistor which works for 1000V and 4mA (Peak inductance current is around 1A) in the collector side while emitter is grounded. Which parameters should I look into to select a suitable transistor ? for the voltage should I be looking into Vbe ? or is Vce enough ...
  22. N

    Transistor Load line doesn't intersect characteristic curves....

    Hello, I've carried out an experiment to plot the characteristic curves (Ic vs Vce) for a BC108 transistor and then attempted to find where the load-line intersects those curves. Below are my results: ...as you can see, the load-line doesn't intersect the characteristic curves at all...
  23. B

    How to calculate Carrier Concentration vs. Depth from a CV measurement?

    I'm trying to obtain the free carrier concentration vs depth profile from the CV (capacitance-voltage) measurements of a normally-on HEMT with the expressions used for a Schottky barrier, but I´'m confused about how to extract the values for depth. I found in textbooks and articles that the...
  24. F

    BJT Transistor Collector Current

    I’ve attached an image below of a section from my textbook and some circuit simulations. The textbook gives an equation for the collector current in a bjt transistor. The simulation shows two circuits (with the same bjt transistor) that hav equal values for all variables present in the textbook...
  25. D

    How to properly use a TIP47G transistor as a switch for larger currents?

    has anybody used a tip47g transistor? i can't get it to act as switch for a larger current. i have tried reading the datasheet. the datasheet won't work.
  26. Terrycho

    (Bipolar Junction Transistor) The Current Gain of Common Base Amplifier

    Everything is okay besides the current gain of this circuit, which is "g" there The formula of current gain is I_out/I_in If I call the current flows to R_e I_2, according to KCL, the following formula must be satisfied. I_in + (β+1)I_b = I_2 Therefore, to know I_in, we should use the...
  27. Peter Alexander

    Engineering Compute the voltage gain of this bipolar junction transistor circuit

    This is the given schematic. The result should be $$A_u = \frac{R_b g_{21}}{1 + R_b g_{22}} = -50$$ and the way I wanted to tackle this problem is by stating $$A_u = \frac{-R_b i_2}{u_1} = \frac{-R_b (g_{21} u_1 + g_{22} u_2)}{u_1} = \frac{-R_b (g_{21} u_1 + g_{22} u_2)}{g_{11} u_1 + g_{12} u_2}...
  28. DamunaTaliffato

    What are the mistakes in determining output impedance using h-parameter model?

    I have this curcuit. I want to discover the output impedance. Using h-parameter model I get the second circuit. I know that Zout= V(open circuit)/I(short circuit) and ie = C ib, where C is an appropriate proportionality factor. Vol = V1 Re/(Rb+Re) = (Rb ib + Re ie) Re/(Rb+Re) Isc = ie = C ib...
  29. C

    Class A Amplifier Sinusoidal Input/Output Relation

    My simplistic derivation below for a Class A amplifier shows that an AC signal at the input produces DC, fundamental, and 2nd harmonic terms at the output. This seems to contradict most the information I have found on this - which just states that the output is sinusoidal and of the same...
  30. P

    Transistor and an LED in parallel

    Hi! I'm new to EE and was wondering if this: https://imgur.com/a/lSgNl52 would cause the LED to light up, or would the transistor short the circuit? (I forgot to add the arrow on the diode and I'm too lazy to fix it. And I just realized that the resistor is wrongly placed.)
  31. 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...
  32. Peter Alexander

    Engineering Computing resistance in given circuit with BJT

    Hi, before you proceed with reading this question, I would like you to know what I do not expect anyone to solve this task for me. I have a problem with a single step in the solution and I'm only asking you to help me with this one step. 1. Homework Statement Compute ##R_B## so that Q-point of...
  33. A

    Voltage Gain of a common-emitter amplifier

    Hi, i have a problem with the voltage-gain of a common-emitter-amplifier. I have calculated the theoretical value of the gain given by ##G=\frac{\partial U_{a}}{\partial U_{e} } = -h_{FE} \frac{R_{c} }{R_{v} }## , which is between -13925 and -7311 for ##420\leq h_{FE} \leq 800## (given by the...
  34. J

    Electronics Make your own transistor tester

    This tester has been in use for 28 years no problem yet. Made out of left overs.
  35. M

    Hello, can somebody check my transistor amplifier schematic?

    Hi, can somebody tell me how to connect some component in this picture, i draw it but is not working because i have no bfg520 transistor, look this picture maybe i make mistake
  36. Delta2

    Ohmic Resistance and Logic gates

    Is ohmic resistance a "necessary evil" in order for transistors to be able to function as logic gates? I mean, I have seen some circuits for the NAND gate in RTL and TTL and they both seem to involve ohmic resistances. Can we make a super conducting NAND gate that will have total ohmic...
  37. D

    Finding the CMOS transistor width ratio

    Homework Statement Calculate the ration of ##w_p/w_n## if n and p transistors in CMOS inverter necessary for the least delay time ##t_p## if the circuit is used in a chain of circuits. a) What is ##w_p## in that circuit if you're given : b) Calculate the maximum short circuit current if...
  38. D

    Engineering Problem regarding a transistor state in a NAND circuit

    Homework Statement Calculate the output function and draw a graph of output voltage in the function of the input voltage of the following digital circuit: Homework Equations 3. The Attempt at a Solution [/B] By analysis of what happens when inputs A and B are on the logical "1" i have...
  39. Voq

    End of Moore's Law? Future of Transistors & Computing Tech

    What are indications for future development of transistors and general computing technology design with the Moore's law in mind? Are we going to redesign architecture for better efficiency and what future brings?
  40. J

    Problems snubbing HF noise on flyback transistor

    Hello, I am working on the design of a flyback converter based on the LT3751 capacitor charging circuit. My design is similar to the 42 A cap charger example on pg. 25 of the LT3751 datasheet. In my case, the circuit runs on 12V and steps up the output to 430 V, but I am having some major noise...
  41. A

    Simulation of transistor switch circuit

    Hello, I'm new to electronics and I'm reading a book currently to learn more about the topic. I'm currently on a section where I'm building circuits where I'm using a transistor as a switch. I decided to experiment with the circuit they gave me and put it in a simulation software called Proteus...
  42. Voq

    Transistor literature (books, links, articles) for learning more about them....

    If you have any material (books, links, articles) on transistors i would appreciate that. I am looking for a way to get more general knowledge on subject. Thank you.
  43. A

    Bizarre Behavior in Discrete PMOS

    Some of my colleagues and I captured the i_D vs V_ds/V_sd curves for the CD4007 MOSFET IC (http://www.ti.com/lit/ds/symlink/cd4007ub.pdf). We did this for the NMOS and PMOS transistors. I have attached the curves to this post. The NMOS curve is as expected. However, the PMOS curve seems to be...
  44. M

    Can somebody tell me the calaculations of this 2 transistor circuit?

    can somebody tell me this circuits calculations, how come 10mA please
  45. F

    NPN transistor and how it operates....

    Hello Everyone, I would to ask you for a couple of clarifications if possible: I understand that a NPN transistor has 3 legs (emitter, base and collector) and that if a very small current goes from the base to the emitter (current ##I_{be}##, the transistor will be turned ON and a larger...
  46. J

    Understanding Transistor Biasing in a Circuit

    Homework Statement Homework EquationsThe Attempt at a Solution This is a solved example in my Physics textbook . I don't understand how this problem can be done without specifying the battery VBB in the Base Emitter loop . The author assumes that the 20 V battery is connected between both...
  47. J

    Transistor : Output voltage of the amplifier

    Homework Statement Homework EquationsThe Attempt at a Solution This is a solved example given in my Physics textbook . I am not understanding a couple of things . 1) How is Iin calculated as Vin/Rin ? Why is the book not taking potential difference between Base Emitter into consideration...
  48. Jayalk97

    Good resources to practice transistor amplifiers?

    Hey guys this isn't so much a homework question as it is a learning question. Any good resources online that could help me practice calculating current/voltage gains as well as input/output resistances for BJT and MOSFET amplifier circuits? I can't really find any resources that give me problems...
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