# What is Npn: Definition and 73 Discussions

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1. ### 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...
2. ### 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...
3. ### Understanding the base emitter voltage in a common emitter NPN BJT

##V_{BE}## is basically the difference in voltage between the base terminal and the emitter terminal. Normally when silicon is used and the transistor is biased to operate in the active region, ##V_{BE}## = 0.7 V approximately. The way I understand this is that for an npn BJT, the applied...
4. ### 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...
5. ### How Do You Solve a Basic BJT Problem Using KVL?

Homework Statement Homework Equations KVL The Attempt at a Solution Using KVL around BE loop 0-0.6-i_e*(30*10^3)-15=0 i_e=-0.52mA However, I stuck when I tried to find i_c and use KVL around CE loop/ CB loop For CE loop: 10-i_c*(15*10^3)-Vce-i_e*(30*10^3)-15=0 For CB loop...
6. ### 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...
7. ### 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...
8. ### Is My Bipolar Base Emitter Voltage Calculation Accurate?

Hi again dear friends. , hope all are doing well. Please could some one evaluate my work and advise me in case any correction is required. Have a good day
9. ### 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...
10. ### 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...
11. ### How to tell if a transistor is NPN or PNP

Today I learned how to tell if a transistor is NPN or PNP:
12. ### What are common issues when using 2N2222 in a BJT NPN amplifier?

Hello people, I am working on a BJT NPN amplifier the model that I've choosen is 2N2222 : http://www.e-voron.dp.ua/files/pdf/tranzistor/2N2222.pdf I am having 3 problems here: 1) am not having any AC voltage at output Vce seems like I have set wrong operating point? 2) I am trying to figure...
13. ### Solve NPN Transistor Puzzle: -0.4V?

I was just sent an email with the following text. "" Here is a puzzle I just encountered. Take any NPN transistor and ground the base. Now apply +12 volts to the emitter through a series resistor of 1k. Yes, it is a Zener diode of about 6 volts so about 6 ma of current flows.What is the...
14. ### Silicon NPN Transistor: Calculating Fermi-Level & Equilibrium Concentrations

Homework Statement we look at a silicum n++ p+ n transistor. given: NE= 1,0×1018 cm–3; NB= 2,0×1016 cm–3; NC = 2,0×1015 cm–3; here E stands for the emitter, B for the basis and C for the collectorHomework Equations a. calculate the distance in eV from the fermi-level to EFi for the emitter...
15. ### Help Understanding Current Gain Of A BJT NPN Transistor

I need to know if my formula's are correct for current gain. Sorry for shakey drawing. I know beta would change the dc values slightly but for my prof. it's close enough. Beta AC = 70. DC Analysis VB = R1R2/R1+R2 VE = VB - VBE IE = VE/RE AC Analysis r'e = 25mv/IE Req = R1 || R2 Rout = RC ||...
16. ### First experience with an NPN BJT

Homework Statement I had a few questions about the npn BJT with regards to designing a few circuits. The questions and my attempts are below. For the calculations, assume ##\beta = 140## and ##V_{BE} = 0.7V## for npn active mode. 1. Fixed bias circuit: Design the resistor values required to...
17. ### NPN BJT in reverse active mode - base current direction

Hi! I was wondering what happens with Base current direction if NPN BJT works in reverse active mode? In forward active and in saturation mode currents are like this: Collector and emitter currents in reverse active mode would be in opposite direction: :
18. ### Is there a way to keep an LED turned on even when the power source is off?

Hi, I'm looking for a device like a transistor which preforms the opposite. E.g. On an NPN when Base is +0.7V current can flow through the Collector to the Emitter and when the voltage at B is 0V (i.e. a switch connected to base is open) no current will flow from C to E. I want the opposite of...
19. ### Basic Electronics: Transistor confusion

So, recently I started learning about electronic components and then I started learning about semiconductors. The one which I've been having some real trouble to understand its function is the transistor. So I bought an electronics textbook called El ABC de La Electrónica (The ABC of Electronics...
20. ### Understanding NPN BJT Transistor: Ic & Ib Ratios

Hi i have have a small question regrading to a NPN BJT transistor. the DC current gain (beta) is the ratio between Ic/Ib where Ic and Ib are the collector and base currents respectively. Ib is the input current, that's alright , but, i don't get why Ic considered as the output? in NPN BJT...
21. ### Can somebody please explain and walk me though this motor drive circuit?

The Drive terminals are connected to a PWM signal generated by an arduino micro controller. The purpose of this circuit is to isolate the arduino from the motors to avoid too much current being drawn. What I understand so far: The motor will only turn when the diode is reverse biased. When it...
22. ### Small NPN 3904 relay style circuit

I am currently trying to make a small circuit work, and more than just trying different things until it does work, I wanted to hopefully get an explanation to why it is not working. I am a novice, I only started dabbling in my free time recently and thought I had a decent if only vague...
23. ### NPN transistor model for use with differential equations-LC oscillator

Hello, I am trying to get a better understanding of how oscillator circuits (clapp, hartley, colpitts etc) work, so I have been trying to solve the differential equation for a very simple one--the one most the way down the page here...
24. ### 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
25. ### About output characterstics of a npn transistor in CE configuration

Q1.when transistor[NPN transistor in CE configuration] is in saturated state ,then,in output characteristic curve on increasing voltage across collector -emitter,the current in the output circuit increases linearly but my confusion is that we know that in saturation state transistor's base...
26. ### Passive Switch for NPN or MOSFET Ideas?

Hi I would like some advice on what you think I should use as a passive switch for my NPN or MOSFET transistor. I am trying to PWM pulse with modulate an electromagnet with a 12V 3.6A battery and I want to have a passive switch. I have tried to use photo interrupters in the past but I am not...
27. ### Current flow in NPN transistor

Here is an image show how currents flow in NPN transistor from Microelectronic Circuits by Sedra Smith: Can you explain more about injected holes (iB1)? I can't imagine how holes can flow into emitter (N type) Is it possible to for holes to flow from base to emitter?
28. ### Questions about npn transistor and operating point of diode

For question 1, it asks me to find the operating point by different methods. But I have no idea to solve it. Can anyone give some hints for me? I can just think about the diode can be replaced by an ideal diode, a 0.5V dc source and a 0.2/4=0.05Ω resistor. For question 3, I have solved...
29. ### NPN and PNP transistors and load

Hello, I've been playing with transistors on a circuit simulator and found that it doesn't matter on an NPN transistor whether I put the load on the collector or emitter side, the load still has the same current flowing through it. The same is true for the PNP transistor, however when I...
30. ### NPN Transistors - Volt/Amps/Headaches

How do I know if a transistor is voltage controlled or current controlled? It seems to me that changing voltage, ceteris paribus, changes the current so what gives? http://en.wikipedia.org/wiki/Bipolar_junction_transistor#Active-mode_NPN_transistors_in_circuits Talking about exponential...
31. ### 2n2222 npn transistor voltage question

So I am working on a project and I am using a diagram I found on this forum but I want to alter it a little. The transistor on the right is a 2n2222 npn transistor. I want to change the 9v to 24v. I've been looking up datasheets on it and I think it will do what I want but I wanted to get a...
32. ### Beta of a Transistor (both NPN and PNP), how would I do that?

Hello, I am trying to design a circuit that can measure the BETA of a PNP and NPN transistor, I have an ammeter, and I have a design that makes IB going in 0.1mA, so that the current IC of the collector with a shifted decimal is the Beta we would like to measure. So I used a current source, and...
33. ### Let's consider npn transistor, when emitter-base is forward with

Let's consider npn transistor, when emitter-base is forward with voltage supplied to it, then the majority charge carrier(electron) will diffuse to base(p-type) , Then (in base-emitter) the minority charge carrier in p-type (electron) will that move close to the depletion layer of...
34. ### Does PNP transistor share the same formulas as an NPN transistor?

The formulas in question are: Beta = Ic/Ib Ie = Ib ( 1 + beta ) Ie = Ib + Ic
35. ### Engineering Convert NPN to PNP Signal - Simple Circuit Diagrams

Hello All, I have a sensor which outputs an NPN signal, however, the gauge it connects to only inputs PNP signals, how can i convert the NPN to PNP? I have tried looking for circuit diagrams and simple converters but I have found nothing, all help appreciate. Thanks
36. ### NPN question typo or my misunderstanding

Ok so I'm reviewing npn transistors and here is what I am looking at http://postimage.org/image/sdywponvv/ Now the book I bought says Ib = (VE + 0.6V)/R1 I have no idea why it would be that Isn't it suppose to be (Vcc -0.6V)/R1 for Ib The transistor is definitely on as emitter is grounded...
37. ### Why Does Base Current Start at 20uA at the Bottom in NPN Curve Tracers?

Hello, Hoping this can be cleared up quickly as I have my final exam in 1 hour. My question is for the attached image. I know for pnp transistors that ic=0, and Vce=0 at top right hand corner. However, one thing I don't understand is why the base current starts at 20uA at the bottom, rather...
38. ### Engineering NPN Transistor Circuit Analysis

Homework Statement Determine the voltage level at V3. For each case also determine which transistors are on and saturated, on and active, and which are off. Let R1=R2=R3=2.2kΩ and let Rc=240Ω and Vcc=5V. Calculate β for each transistor as well. We are to assume that if the transistor is on...
39. ### IC 74192 and low power MPSA 14 NPN TRANSISTOR

HI FRIENDS Is there any substitute of IC 74192 and low power MPSA 14 NPN TRANSISTOR I Cat`t find that in my country. thanks
40. ### Identifying PNP and NPN Transistors

Hello, I just bought lot of pnp and npn transistors. They are not labeled. How do i tell them apart?!
41. ### Gain of an NPN Transistor: Understanding Ic/Ib

If the base current of an NPN transistor is increased, what will happen to its Collector current since I still don't understand how a transistor amplifies signals or about the current gain. (i.e. Ic/Ib)
42. ### Bjt npn base collector junction breakdown

When the NPN is in the forward active mode The base emitter junction is forward biased and the base collector junction is reverse biased. But isn't it possible for the base collector junction to break down? Or do we assume it never breaks down? Also does anyone know any good water analogies...
43. ### NPN Transistor - Sink or Source?

All electron flow nuances aside, let's look at simple circuit analysis. Hopefully you guys can clarify something for me. Say we have to drive an LED. We have a +5V source, a 3.4V forward voltage, and a 150 Ohm current limiting resistor: +5V --> Resistor --> LED --> GND Okay, so let's...
44. ### What is the Function of a Diode in Protecting an NPN Transistor?

Homework Statement The absolute max voltage rating for the base-emitter voltage is the lowest of all values. This low value means the B-E junction must be protected from a high reverse voltage. A diode is used for an npn transistor. Explain its function and conditions under which...
45. ### NpN bipolar transistor current gain

I have been studying npn bipolar transistors and how to apply gain to the current in a circuit, yet i simply do not comprehend how altering the base - emitter current can effect the emitter - collector current, can anyone here explain how altering the base - emitter current effects the emitter...
46. ### Calculating NPN Transistor Vin: Exploring the Minimum Input Voltage Requirement

Homework Statement What is the minimum input voltage for which the transistor will begin to turn on? Homework Equations None. The Attempt at a Solution I don't understand why the answer was 0.7V. I understand that yes by the time you reach the base there will be 0.7V left which...
47. ### Help with design - NPN High Power BJT

Hey folks, First time poster. I'll try to be as specific as possible. We have been working on our senior design project for one semester and we have a semester remaining. We came to a snag after being very successful with our design. Essentially, we're using an arduino deumilanove micro...
48. ### Determining Part Number for NPN Transistors

hello good day, would someone kindly help me determine the part number of these 4 npn transistors here? pls help, cause my prof didn't discuss this yet.. and i don't have idea on how to calculate for the values of the transistor to determine tha part number suitable for the circuit... many...
49. ### Understanding PNP and NPN Transistors

Homework Statement revered members, in the following attachment, i could work out the path of current in pnp transistor, that is, from base through RB AND THE output is taken across RL. but i can't figure out the path of current in npn transistor. could u please help? Homework Equations...
50. ### 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...