Search for npn in Topics


Resistors for a NPN transistor? Answered

In the circuit diagram(which I've uploaded),I intent to use a NPN transistor(BC 547) as a relay.The 9 VDC is stepped down to 5 VDC by a LM7805 and should be the trigger to the transistor,completing a circuit which needs the 9 VDC.The Collector is given the common negative of both the voltages and the trigger gets the positive 5VDC.I need a bit help to calculate R1 and R2.I had used two random resistors previously but the Load got powered by the 9 VDC even before the trigger was applied to the transistor.I figured out that the problem might be related to the resistors used. (I haven't included the caps used at the terminals of the regulator in the schematic)

Question by Adarsh_tronix    |  last reply


NPN to PNP control? Answered

So as I get into this project the circuit keeps building and now I once again have another problem that I can't figure out. As the title hopefully suggests I am using a NPN PN2222A trans. to control a PNP 2N3906 The idea was to use the 5v from a Ardinuo UNO to control a 12v. Currently I am testing with a 9v I had on hand. I thought it would pretty straight forward but every time I supply power to the NPN it creates the short needed to turn on the LED, but once I cut the power the LED stays on until I create another short (using a probe) uphill of the NPN. The only thing I can think of is that the LED doesn't the resistance needed for the power to re-saturated the PNP. Any thoughts? I will admit  haven't done any of the math needed yet for the resistors. Also can someone send me a link to the programs you use for drawing the layouts so I can move past MSpaint?

Question by Jayccob    |  last reply


Choosing a transistor (NPN)? Answered

Hey Guys, Recently I was ordering electrical components online and when I reached transistors I couldn't choose any. I was wondering that can I order any transistor or will it ave to be specific one? I need one for projects like wireless induction, laser tripwires etc. I would really appreciate it if you could help. Thanks in advance -Prickly Potato

Question by The Prickly Potato    |  last reply


NPN BJT strange behavior? Answered

My linear power supply design has been using a PNP MJE2955 pass transistor wired to a 2N4401 as a complementary darlington configuration, but this was not an inherently stable design, and would oscillate when adding output smoothing capacitors, particularly MLCC types (with very low ESR). So I decided to try the far more common darlington arrangement, although I am not fond of the higher voltage drop. However the output was oscillating at approximately 3KHz with 1uF output capacitance, with NO input to darlington. I removed the 2N4401 so all I had left was just a 2N3055 transistor with the emitter connected to the output and the collector connected to a 20V supply. The output was ringing like crazy. The oscillation frequency could be changed by adding/removing output capacitance. Why is this happening? How should I go about stopping this oscillation? I originally had a 4.7k resistive load on the output but it did not significantly affect the output oscillation.

Question by -max-    |  last reply


could i make a transistor by stacking 3 silicon wafers, N type P type N type?, and soldering wires to them? Answered

Was reading about homemade transistors, but it is really complex, so would this work?

Question by pwnag3    |  last reply


npn transistor and impedance question? Answered

Hello , i have question about transistor .The picture below is a simple npn transistor booster .Can you give me the formula of gain and output impedance of this schematic please. Thanks! sorry for my bad English!

Question by login721    |  last reply


NPN trasistor tutorial help

I was going to try to make a transistor tester for npn's and I wanted to know a little more about them. Please give me information about this. Whoever helps me on this I give a big thanks to. Also list some projects you made with it. I'm always looking for good ideas. If you have any comment on my question or leave a comment on one of my instructables. Thanks!!!! project_builder

Question by project_builder    |  last reply


Resistor for NPN Transistor Base? Answered

Hey all, I need help identifying the value of the resistor I would need for the base of a 2n2222a transistor in this circuit. If you need any additional information, ask and ill try to answer asap. The resistance of the relay coil is 106 ohms and its rated for 6v but I operate it at 5v. The 3.3v is supplied by a step down circuit connected to the same power supply as the 5v used to operate the relay. If you can, please also list the steps you took to calculate the value of the resistor so that it can be useful for future use, I couldn't find a simple answer online. Ty,

Question by SA-DIY    |  last reply


What practical applications do PNP and NPN transistors have? Answered

I read about NPN and PNP transistors and I was wondering what type of applications are right for each type of transistors. I understand that depending on the type of transistor the emitter should be connected to either an anode or cathode.

Question by blkhawk    |  last reply


Where can I find NPN (2N3904)Transistors in scrap/unused electronics, in what devices can they be found in?

I would like to know where I can find an NPN (2N3904)Transistor inside of something I may already have. 

Question by ArtTech86    |  last reply


Transistor battery question

Hi, I want to know if I can hook up an 18v 3ah battery to a npn transistor with a max of 1a. Will the transistor only let through 1a or will it get burnt out? Thanks.

Question by RyanF191    |  last reply


Transistor question

Hey guys I have a question on transistors. When using for PWM setups, is the difference between each NPN (or PNP) transistor model by its specs? Such as gate voltage, max current, etc. I am making a LED touch setup made by qs, but I want to make it so that the Arduino activates a transistor to turn on a string of lights that the arduino could not power on its own. Here is the setup of the LED string. I want to replace the TIP31 in the wiring diagram with a NPN transistor (like this one). By replacing it, which pins go to which wire and do it have to add anything else to the setup? Will the new setup also work with PWM signals? Thanks! KT Gadget

Topic by KT Gadget    |  last reply


what is a correct resistor to use on a 2n3094 transistor? Answered

Im connecting it to a Positive 9volt signal for a distortion

Question by fatfoohy    |  last reply


Where can I get a MPF Transistor?

Hey guys, I wish my local store had more stuff but it is kind of bad... Does anyone know where I can find or get a MPF, I bought a NPN transistor instead do you guys think it will work? I am making a sound amplifier, are there and equivalents if I don't find the MPF? Thanks, Tobias

Topic by TobaTobias    |  last reply


2x bipolar transistor? Answered

If I took 2 similar NPN transistors and connected both the bases together, both the collecters, and both the emitters, then put it into a circuit, what would the 2 transistors do? Would the maximum power dissipation be increased or something? 

Question by .Unknown.    |  last reply


SMT variant of 2N3904 NPN transistor? Answered

Im looking for a SMT equivalent of a 2n3904 transistor. I found one on digikey that might be similar, the MMBT3904. Is this correct? Many thanks- Astroboy907

Question by astroboy907    |  last reply


help with using a transistor npn as a switch

I am some what of a noob in electronics. I wanted to know if i am able to you a transistor for a camera switch. I have TIP31 npn transistor. what i am trying to do is using arduino to take pictures every 10 seconds or so. I know this could be done with relays but i just wanted to learn how to use transistors and how they work. any help would be great. or links on what i am trying to achive here. big thanks to every one

Topic by DELETED_kclv1988    |  last reply


variable frequency drive construction?

Hello i am working on a go kart but instead it will be powered by a 1/3 horsepower split phase AC motor. it operates off 768 watts and i am curious in using a Microcontroller and a high power H bridge to control it. can anyone help me or give me an idea on how to step up 12v dc into 120v dc and then using the H bridge to generate the frequency and also where to find some NPN transistors that can handle it and how to possibly reverse the direction of the motor?

Question by luig    |  last reply


Need help with JFET preamp and chossing transistor ? Answered

Hello .I'm having some some problems with my current project .Can you guys help me please ! This is the schematic of MXR headphone amp for guitar .I don't have 2n4401 and 2n4403 , so i replace them with 2n3904 and 2n3906.The result is output is too low .2n4401 and 2n4403 (collector current = 600mA) ,2n3904 and 2n3906 (collector current = 200mA).If i replace the transistor with higher Ic i will have louder output ??? http://i247.photobucket.com/albums/gg132/chipmapple/mxrheadphoneampschematic.gif Thanks for advance! Sorry for my bad English!

Question by login721    |  last reply



Logic Gate Help Needed Answered

I am building a Binary to Decimal converter and i need help making a flawless AND gate from bipolar-junction transistors. If someone could Send me a link or email me some schematics, I would greatly appreciate it. If you do email the schematics please make sure they are compatible with Eagle. I don't want to use a converter chip because it takes away the fun of the project for me. I have tried all of the common types of AND gate configurations using NPN's (C-fwd B-in E-collect, C-in B-fwd E-Base, Etc.).

Question by toast5678    |  last reply


Triggering a device remotely through bluetooth? Answered

Ok, so i was hoping to set off an electric match using two phones and bluetooth. i hooked an NPN transister up so that when low voltage is applied, it triggers the high voltage output which goes to the electric match. sorry if im paraphrasing here, i hope someone out there understands what im meaning to say. anyways, what i want to do is have an app that works through bluetooth to provide the low voltage i need through the usb which hooks into the npn transister. in other words, a phones usb triggers low voltage place on transister which then gives the higher voltage output. and it does so by using bluetooth to keep it remote. so again, bluetooth triggers usb, usb triggers low voltage place, then that place lets the high voltage go through. let me know if i need to clear up anything and im very sorry about the grammar but ive been racking my brain over this and its 4 am where im at, and i got no sleep. therefor-- too tired to correct spelling errors. any help is appreciated, thank you!

Question by XBLmonster    |  last reply


How do i know if a transistor is npn or pnp????

How do i know if a transistor is npn or pnp???? plz HELP

Question by Dannne11    |  last reply


Will tip31c work for music leds? Answered

I am interested in this: www.instructables.com/id/Music-LED-Light-Box/ Will tip31c work rather than tip31 www.datasheetcatalog.com/datasheets_pdf/T/I/P/3/TIP31C.shtml I'm hypothesize that it will just affect sensitivity. (more or less?)

Question by Dmxspider    |  last reply


How do i know if a transistor is of PNP or NPN type?

I want to know how to recognize the type of transistor.

Question by bishal    |  last reply


can any NPN transistor be used to make joule thief.....and 1kohm resistor is only necessry to make it???????????

Iam making joule thief....................can i use any Npn transistor to make it and only 1kohm resistor be use???........is it work on different value of resistor.............?????????

Question by rachit59    |  last reply


Can I use any npn transistor on this instuctables? Answered

Https://www.instructables.com/id/Blinking-LEDs-to-Music/

Question by theVader75    |  last reply


I have 14 NPN type switching transistor, what can i do with them?

I need some simple project(s) to use them up.

Question by XOIIO    |  last reply


Transistor Swithching Voltage? Answered

Looking at this data sheet: http://www.datasheetcatalog.org/datasheet/stmicroelectronics/4136.pdf How much voltage has to be applied across the base and emitter to switch on a "TIP 3055" transistor? The V-be row is the only thing that looks like it is telling about that, but I don't think that's what I'm looking for (mabey it is?).

Question by Jaycub    |  last reply


How Do I Make LED's Fade with an already build flashing circuit? Answered

Hello everyone! In my spare time I've built a simple circuit which makes an LED flash. The flashing is controllable through a Potentiometer. I have attached a circuit diagram (made really fast, so i know it's bad) and the picture of the breadboard. Now, my question is: How can I make the LED fade on and off instead of flashing? I've tried to hook up a transistor but i've not succeeded. If everyone could help, I'd appreciate it. Here is the stuff I think could be useful that I have avilewable: Some BC 144 Transistors (I suppose they're PNP) Some PN 2222a Transistors 220uF Cap, 100uF Cap and a 10uF Capacitor. A lot of resistors. I do have more components but I don't think they could be used for this project. And excuse me for any mistakes, English is not my Language, Thank you!

Question by Reogen    |  last reply



Can a 2N3055 transistor be operated at voltages under 60v ? Answered

Can the minimum collector emiter sustaining voltage of a transistor be more than the power supply voltage or is that somthing else? For example can I run a transistor with a minimum collector emmiter sustaining voltage of 100 with a 12 volt power supply ? Thanks

Question by build a BOOM    |  last reply


AM transmitter design ??

Is it better to use a diode for DSB SC modulation for good range ? or it's better to use npn transistor ?

Topic by walidj    |  last reply


Substitute of Power Transistor

What is the substitute of 2N6292 power transistor? Please suggest a good substitute of 2N6292.It must be an NPN power transistor. Thank you.

Question by SiamB1    |  last reply


Does anyone have a 28 LED Diagram Using Photocell & NPN Transistor?

I am new at electronic engineering but i just have a few questions about a diagram i tested which seems to work, but i rather more opinions to ensure my transistor, or leds, or resistors, or anything else doesn't burn out but last. Can someone advise me if i need to change any resistors? I need some guidance please. Thank you for the help, its really appreciate. In the future i may be downgrading to 5MM LEDs...Red & White. When i do downgrade, will i need to replace my resistors? MY circuit is in parallel..Should it be a good idea to switch to a Series Circuit instead?

Question by islandboii242    |  last reply


how exactly do transistors work? in detail.? Answered

 i need to know about how applying a positive charge to the base allows electrons to flow through it to the emmiter. npn

Question by 2tautges    |  last reply


Will this 'switching' circuit work for cabinet lights? Any comments?

Im making cabinet lights using LEDs. I use a transformer to power it off AC mains, but I want it to run on batteries too... So Im making a circuit that would automatically change the source of the power from the mains to battery when the power goes out, and back again when it comes on. Im using an NPN and a PNP transistor to do the switching. When mains (S1) is on, the NPN is on and current flows from the transformer, when S1 is off, NPN is off and PNP is on and current flows from the batteries. What I am worried about is that (I think) the transistors need a Gnd on the emitter. Is that right? If I connect the +ve of LEDs to [OUT] and -ve to GND will it work as expected? Can someone try please?

Question by pro2xy    |  last reply


How to control more positive current using microcontrollers?

Most microcontrollers can directly control low current  at +5v. Using NPN transistors I can control higher currents, but now negative. My question is: how to switch more positive current (>40mA) than my microcontroller can do directly? The obvious idea is to cascade a PNP to a NPN transistor, but aren't there ICs ready-made for it? More or less like UNL2803A, but using Sziklai arrays instead. What would otherwise be the "standard" way of doing it?

Question by eshneto    |  last reply


HELP: Blinking light circuit ( Music Synced)

Hi I'm trying to build a music synced blinking light circuit. However I AM A NOOB. I don't know almost anything about electronics and stuff. But i'll manage. So the first problem is that I cannot get tip31 or any tip transistors in the market. All I have is BC547 NPN transistor or 2N2222, General Purpose NPN Signal Transistors ( TO92 ). And I wish to attach blue led strip in the circuit. and will be powering the circuit using 12v power adapter. Please suggest how much of Amps should it be of. A diagram of it would also help :) Thanks in advance!

Question by vmahajan3    |  last reply


Witch transistor should i choose for low noise audio ? Answered

Hello , im making a guitar pedal .The original schematic use transistor BC107B (epitaxial NPN) but i dont have it.so i find some other NPN transistor to replace it. I have 2N3903 ,2SC1815,2N3904 , but witch should i choose for low noise application ? in their datasheet i found the "NF : noise figure" , the lower NF mean lower noise ?? BC107B         NF  Typ.= 2  Max.= 10 2N3903          NF  Typ.= -  Max.= 6 2N3904          NF  Typ.= -  Max.= 5 2SC1815       NF  Typ.= 1  Max.= 10 Thanks for advance! sorry for my bad English.

Question by login721    |  last reply


Electronic Circuit

I have a spst relay(operating voltage-12v) using for switching the solenoid valve(24VDC and 0.5Amp) which connected through 24 V battery. relay is again connected to the transistor BJT NPN . So please suggest me that which transistor is most suitable.

Topic by jay_3189    |  last reply


will an sts transistor work with an led cube powered by arduino?

sts 1979 f2 transistors I know I'm supposed to use npn ,but I have sts 1979 f2 transistors and sto 1862 te3 transistors on hand.

Question by the_burrito_master    |  last reply


WHICH ONE? Answered

TODAY I GOT A CIRCUIT THAT'S A USB BLINKER CIRCUIT I FOUND THE TRANSISTORS ARE NAMED LIKE THIS " 2x NPN General Purpose Transistor (Q1, Q2) " I DON'T KNOW WHICH TRANSISTOR I WOULD USE TO MAKE THIS CAN ANYBODY ELABORATE??

Question by ubdussamad    |  last reply


Replacing the 2N3904 with an SCR

So i made a laser alarm system some time back, it worked good but had one fault, more like a limitation. it made the buzzer ''buzz'' only when the laser was interrupted and the buzzer turned off when the laser was allowed to hit the photo sensor again. i wanted it to stay on until turned off by a switch. someone suggested something called a monostable flip flop but i had no idea what it even meant, then i saw something called silicon controlled rectifier or a thyristor, but i also learned that they have to be made using a pnp and npn transistor, what i cant understand is what transistors should i use to replace the npn transistor on my circuit, the tansistor on my cicuit is 2n3904, input voltage is 5v

Question by walee    |  last reply


Can i make a LED to fade with music?

I want to have a LED alwais on and with the tempo of the music the LED will turn off or fade. to make this i have a npn a pnp and a SINGLE OPERATIONAL AMPLIFIER the led is 3v. i don't have an Arduino o another tipe or controller

Question by clowreed    |  last reply


Help with simple transistor circuit.? Answered

I want the LED to turn on when it's dark. But  it remains on and taking out the LDR doesn't affect it. I couldn't post a picture but i made a replica in Fritzing EDIT: The transistor is 3904 NPN.

Question by Hafiz Mohammad Shayan Tariq    |  last reply


Transistors are best for melting brains!!

I have been experimenting with transistors for 3 days now, both NPN and PNP. So far I have concluded nothing. I figure the easiest thing to do is to make a transistor work as a switch. With the NPN, the current seems to flow from the base to the emitter automatically. My understanding is that current should flow from the collector + to the emitter- only when I apply voltage +? to the base, is that correct? I don’t even need to connect the collector on the NPN and current flows. I have also read a million things about transistors online. My experiments seem to disprove most(all?) of the findings. This leads me to one conclusion. I’m not doing something right. Maybe I don’t have the right transistors. I have no idea. I have been using radioshack NPN’s (276-2016) and PNP’s (276-1604) When it tried to make a switch with a PNP my voltages was going back through my emitter to ground. If I disconnected it the system(test led) no longer worked. You might need to know that I was using a 5v voltage regulator to supply a 10v 5v and ground leads for my experiments. I was getting odd voltage readings on my circuits so I put diodes on the leads. The diodes stopped my PNP from working(I figured the current was flowing odd ways…back in the 5v+?) and didn’t seem to effect my NPN experiments. So I figure I’m closer on my NPN’s than my PNP’s. I wish I could explain better but my brain is about to melt. My wife is mad at me because I am obsessed with making this work… please help :P

Topic by kendallickes    |  last reply


stop 7-segment from ghosting?

I'm working on a simple arduino 7 segment driving circuit. (It also has a led bar-graph that displays binary numbers but that part is working fine.) When I get the display working I might make an instructible out of it. Here's the basic layout: -using this 8 segmet 4 digit common cathode display. -arduino controls what segments are on via 74HC164 8-bit Serial Shift Register -shift register controls an array of 8 PNP transistors with base and pull-up resistors -transistors connect to display anodes through resistor array -display cathodes (common for each digit) connected to array of 4 PNP transistors with base and pull-down resistors  -PNP transistors controlled by arduino. (I will post the schematic shortly.) In software, to display a four digit number, I shift the pattern for a given digit to the shift-register, which in turn turns on the PNPs for the corresponding segment anodes. I then turn on the NPN for that digit's cathode. I delay for a few milliseconds, then turn the NPN off, shift the next digit in, and turn the NPN for that digit on. Rinse and repeat. It works fine but the segments that should be off are at about 1/2 brightness, making all the digits look like eights. Even the DP looks like it's on and I'm not turning it on anywhere. Do I need pull-down resistors for the anodes or something? What's going on here?

Question by Vick Jr    |  last reply


what is this transistor?

I found this transistor in an old genius ps2 mouse (the connection not play station!) it looks like any normal one i've searched google and data sheets searching for it nothing came with any information (one of them said this is a DC motor!) written on it: 536 f   1A exactly. so is it npn or pnp is it power,audio,or general purpose

Question by top.boy    |  last reply


Thermal Flashlight scaling help

Hello all, I'm dont have much basic knowledge about electronics and I got a problem. I've built this exact Instructable: https://www.instructables.com/id/Build-a-Thermal-Flashlight-Light-Painting-with-T/?ALLSTEPS I want to drive a 1m RGB LED strip with it so I've changed the NPN transistors to stronger ones that handle 0.5 A, it's the only components that are different. These are the exact NPN transistors: https://www.elfa.se/elfa3~eu_en/elfa/init.do?item=71-014-58&toc;=0&q;=BC337-25 Problem: the circuit works fine with ONE RGB LED but it does not work with even the smallest bit of RGB-strip (3 emitters). Goal is to drive a 1m strip and that consumes 14.4W @ 12V. Im using 12V 1A adapter for the Arduino and another 12V 2.5A for the LED-strip. What am I not understanding?

Topic by ronnlund    |  last reply