Finally got around to learning about transistors and this is by far the best transistor site I came around. Feel free to add all you know about how to use different types of transistors around the site

Posted by guyfrom7up 10 years ago

help w/ transistors

Does anyone know a good experiment to teach what transistors do? I have read everything I can find about them and I still don’t understand what they do and how they do it. Can anyone help?

Posted by kendallickes 9 years ago

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

Posted by kendallickes 9 years ago

Do they make PNP Transistors that can handle 3.3A

Do they make PNP Transistors that can handle 3.3A

Posted by kendallickes 9 years ago

Where do i get photodarlington transistors or equivilent?

Where do i get photodarlington transistors or equivilent? anyone know? to be clear it basically looks like a black led with a + and - unlike most transistors that have 3 prongs this only has two. when light hits it, it allows current to flow.

Posted by kendallickes 9 years ago

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

Posted by DELETED_kclv1988 10 years ago

peltier circuit board

Circuit board I need to make a circuit board for a project. It is all 12vdc, I have a 1a fan and a 6a thermoelectric device one setting 1, plus another 6a on setting 2, and a 3rd on setting 3 So 1 is 7a 2 is 13a 3 is 19a How to make the board. Also a second device has the 1a fan plus a 4watt element, plus another 4w on setting 2, plus another 4w on setting 3 So 1 is 1a and I think 0.4a= 1.4a 2 is 1.8a 3 is 2.2a. I think

Posted by Johnieahenderson 1 year ago

how to make a circuit board

Circuit board I need to make a circuit board for a project. It is all 12vdc, I have a 1a fan and a 6a thermoelectric device one setting 1, plus another 6a on setting 2, and a 3rd on setting 3 So 1 is 7a 2 is 13a 3 is 19a How to make the board. Also a second device has the 1a fan plus a 4watt element, plus another 4w on setting 2, plus another 4w on setting 3 So 1 is 1a and I think 0.4a= 1.4a 2 is 1.8a 3 is 2.2a. I think

Posted by Johnieahenderson 1 year ago

Transistors in series

If I were to put transistors in series (and hook up there bases together through proper biasing resistors) would it increase the voltage capacbility of the circuit? I need a way of switching on and off about 1000 volts really fast. for example, would 2 750 volt transistors in series be able to handle 1500 volts or not? just a HV pic from my old, dead NST

Posted by guyfrom7up 9 years ago

AC187 Transistor Alternative???

Hi I was wondering if anyone knew of any Silicon or Germanium alternatives to the AC187 Transistor. Also is the BC548 or BC547 Silicon Transistor an alternative to the AC187 Germanium transistor?  Thanks in advance

Posted by Ikram1ali 3 years ago

identifying transistors

Hello all, i have a lot of transistors that are mixed up. how can i ID them? example: on the front markings are .BC 7-25 014. and on the back is the letter Q what transistor is this?

Posted by sasarchiver 6 years ago

Complementary transistors

What or which PNP Complementary transistor can I use with a N-Channel  IGBT HGTP10N120BN 35A 1200V NPT   Transistor  ? I really will thank you . I'm building an H- Bridge motor drive. Ed.

Posted by DELETED_applegoose 6 years ago

SS8550 D331 Transistor

Hi , Guys can you tell me if  2N2222 Transistor is equal ant to SS8550 . It's in an IR circuit . Thanks in advance :D

Posted by UsmanK14 2 years ago

What is a transistor ?

What is a transistor (( can it transform voltage for example from 5v to 12v ?? )) Which component can transform low voltage to a little higher voltage ?? Thanks !!

Posted by yousouf 6 years ago

Transistor relay with NO and NC?

Does anyone know how to make a solid state relay with a NO contact and a NC?Does anyone have a schematic?Thanks.

Posted by thermoelectric 9 years ago

help picking transistor

Me no get no transistors. me need help. me using ltc4060 chip and me need help picking the pnp transistor. heres datasheet,C1,C1003,C1037,C1078,C1088,P7601,D5235it's on page 14 - 15I'm using 3 cells and a charge current of 35 mABTW I'm not stupid, just never really got how to use transistors

Posted by guyfrom7up 10 years ago

overheating transistor on DC motor control circuit

I am trying to control a DC motor using 4 transistors, i am using 547 transistors connected to a motor with two on each axis, the opposite corners are wired together with two pushbuttons, the transistors change the polarity of the motor so that if one button i pressed the motor spins one way, the other button vice versa, but the motor is running very slowly in this setup and the last two transistor that go from the motor to ground heat up very quickly. the circuit works fine with only one transistor but i want to be able to change the direction of spin, does anyone know why the transistors are acting like this or a better circuit to control a DC motor? thanks very much!

Posted by sholtob 6 years ago

Transistor switching problem

I am having trouble using transistors to switch a some LEDs, I have 5 LEDs in parallel being switched by one transistor but each LED is indervidually switched by another transistor. I have given each LED its own resistor and the problem I am having is that when all LEDs are on each LED gets dimmer then if only one was on. I don't really understand why this is happening but I'm not 100% comfortable with transistors and I have probably done something stupid. I have attached a image of how I have wired it up with only two LEDs

Posted by camlv 8 years ago

TIP31cg transistor

HI all, im trying to make this project, a led box that flashes to music i purchased a tip31 transistor, but when i got home i discovered it was a top31cg. is this going to be a problem? thanks all!

Posted by i-like-cheese 7 years ago

DC buzzer/noisemaker that doesn’t use a transistor?

I’ve got some nice homemade field phones I made out of old carbon microphone handsets.  I’ve currently got DC piezo buzzers for ringers (which have transistors in them). I want to them to be able to survive an EMP, so I don’t want to use transistors. Is there anything I can use for a DC buzzer/noisemaker that doesn’t need AC power, or a transistor?   The voltage of the phones is 1.5v - 3v dc    

Posted by instrucables360 2 years ago

How to use a transistor with many LEDs

Hey! I was wondering I want to 1 pin on my ATtiny2313 to turn on 10 LEDs at once, but I know that I should have that many LEDs hooked up to the same pin. Can I use a simple transistor (3904, 2N222A) as a switch? Sorry I am very ignorant about transistors and capacitors :D

Posted by HavocRC 4 years ago

What does mpsa transistor mean?

I have a project that requires mpsa13 transistor but the local electronics shop only carries mpsa12 i don't know what is the difference between the two, what are some alternatives or do they have different names in different country. thanks in advance

Posted by MaxF5 2 years ago

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

Posted by KT Gadget 8 years ago

How do Transistors handle Amperage?

Hey, I'm working on a wireless power transfer system and I'm planning on running it on 12vdc with a 2n3904 transistor, but my power supply supplies 2 amps. Now the question is, will the transistor draw only the current that my transmitter coils draw, or will it simply draw it all for supplying the coils. I have not yet determined how many turns or what resistance they have yet, I'm still in early stages. I just don't want to ruin one of my few transistors. I know the absolute maximum current this specific transistor can handle is 200ma.

Posted by DecemberRain01 2 years ago

help with transistors

Could someone tell me if this will succeed in keeping itself on if the button is hit once?

Posted by James (pseudo-geek) 11 years ago

Tip31 Transistor alternatives

I teach middle school science, and I'm helping a small group of keen students work on DIY projects.  One of the students wants to try this: It calls for a Tip31 Transistor, which is proving difficult to find, at least in Canada.  The comments section suggests at one point that any NPN transistor will do. Can anyone confirm this?  Or can you suggest more readily available alternatives? Thanks!

Posted by dochockin 2 years ago

Transistor Trouble

Hi there, I have been working on controlling a large toy car with a wireless receiver from a smaller toy car, the motors I need to control are rated for 9V but the receiver only outputs 3V, reversing polarity to reverse the motor. I made this schematic using transistors to handle the voltage, but when I built the circuit the transistors began to heat up and there was no output. I am not sure why this is happening, so any help would be greatly appreciated. Thanks, Daniel

Posted by daniel12354 2 years ago

Transistor Substitute

Hey! I'm attempting again to make a wireless FM transmitter. The project plans call for a BC547C transistor, which is pretty common but I don't have any. Can I use a 3904 or a 2N222A instead? Thanks!

Posted by HavocRC 4 years ago

Need Electronics help

Anyone know a simple circuit that will let me test to see if my transistor is burned out?

Posted by Shadowmang 9 years ago

Quick Transistor question?

I am using pnp transistors as switches. I finally got a working prototype!!!Anyway my prototype motor runs at .18A and the real motors I want to run are 3.3ACan these PNP's handle that? can you tell me how to figure that out so I'm not always asking simple questions?Thanks!

Posted by kendallickes 9 years ago

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.

Posted by jay_3189 4 years ago

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

Posted by TobaTobias 6 years ago

why use a transistor when i can use the I/O pins of an ardunio

I keep seeing explanations of the uses of transistors for electronic projects. but i dont understand why i would for example: use a npn as a switch for an LED when i could just program my ardunio to use to turn it on and off again? or use any micro controller for that matter. thankyou in advance for your help im still new to eltronics

Posted by JoshuaH171 1 year ago

Transistor as switch with low leakage current

I don't really know much about transistors, alas, but I am looking to use a transistor as a switch in a device where it's important to me to that the batteries (3xAAA) last about a year. This means that I want to minimize leakage current. I would like to use about 20 mA at 2.7V to control 0.5-1 A at 3.3V (I have 4.5V at my disposal, so I can handle a 1.2V drop through the transistor). The device is a water leak alarm which I assume uses almost no current except when it's alarming. Any suggestions on what to use?  A lot of people use TIP120s as switches, but I've also seen comments that indicate that they have an unpleasantly large leakage current. And I don't need the high voltage/current/amplification capabilities of the TIP120. Or should I just use a solid state or electromechanical relay?

Posted by arpruss 3 years ago

latch with timed variable reset using transistors

I made a 555 t flip flop and it works nice (i use it as a light switch in my room), but i would like to add another button, whet i pres it would turn the light on  for a time and then automatically off after some seconds to minute. can anyone help me?

Posted by bugijs123 6 years ago

Transistor help

I got a 5M LED Light Strip. Its controller say it needs 12V 2A but each LED uses 20mA each and there are 300 in this strip which = 6A. I want to cut this strip into 4 segments and power each one using an arduino. 1 strip = 2.1A 2 strip = 1.26A 3 strip = 1.5A 4 strip = 1.14A =6A My question is do I need different transistors for each strip because of the difference in amperage or can I use the same one? If so, which one!? Thanks for your attentions. Bobbay

Posted by Tzla 6 years ago

One Transistor Based Code Lock

Hello All, i have tried really hard to search for a Instructable based on the above topic, i do remember that i saw it in this site but now i cannot find it, the circuit is, please link me to this Instructable, i would be really thankful to all of you. ALSO HOW CAN I ADD A BUZZER WHEN A WRONG CODE OR COMBINATION IS ENTERED.  ALSO WHAT TYPE OF SWITCH OR PUSH BUTTON SHOULD I USE PLEASE GUIDE ME.

Posted by khan12 5 years ago

Transistor Voltage Inverter

I am a newbie and was hoping someone could assist me. Given the following schematic which takes a voltage of 12v and considers it off and a voltage of 2 volts and considers it on can someone tell me what changes would need to take place regarding capacitors and resistors (if any) to account for 20v instead of 12v? Meaning that when 20v is considered off and 2v is considered on.

Posted by TimothyE2 3 years ago

SMD components codes

Its my first time using smd components i bought some transistor but i dont know how to identify itcode written on it is 3ft22what transistor is this and how you read code like these ?

Posted by DabuHackker 2 months ago

Help with wiring TIP31 transistor to run LED's on subwoofer?

I am wiring LEDs to my subwoofer to sync in beat of the music, to stop the bulbs from blowing, i am thinking of wiring a TIP31 transistor to it and plug in RCA and 12v in to run it using a rca out to the actual amp, in the attached picture please make sure i got all the wiring right and tell me if it would work id get a bigger picture but it wouldnt let me, just use like browser zoom or open in paint

Posted by daleumad 6 years ago

Need help: Transistor 7805 problem

Hello . I just make a PSP charger. I used a 12v,450mA adapter as power source and a 7805 transistor to get 5v output. this is the wire map: When i plug it to my PSP, it's work, but the Transistor start become hotter, after 2mins the transitor is very hot... I don't know what's wrong with it, i tried other 7805 but got same problem. Please help.... Thanks very much .! *sorry for my bad English

Posted by login721 7 years ago

Must have capacitors, resistors, transistors

I am wanting to know the best values/ most used values in electronics projects for resistors, capacitors, and transistors. Suggestions? Also when purchasing capacitors, ceramic vs. electrolyte? Are ceramic mostly for lower capacitance values? And lastly what is the difference between a 10k resistor and a 10 Ohm resistor. What I have figured out is that the 10k is a higher resistance value.  Thanks, diamondmine

Posted by diamondmine 4 years ago

Wondering What Kind of aTransistor I Need

I'm looking for a transistor that can control 12V from arduino which I believe is a 5V signal? If I'm wrong, I need what it gives off but I'm looking for one to control motors that are 12V. Thanks!

Posted by MackeFeet 5 years ago

designing and building power supply using pre amplifier and darlington transistors

am doing a project on building a power amplifier driven by a pre amplifier with normal darlington complementary power transistors for school and i have no idea of where to start with.HELP PLEASE sandra

Posted by sandy23 7 years ago

disposable camera charging circuit

Why doesn't the transistor in the inverter circuit of the disposable camera ever heat up? dont they need heat sinks? can anybody pls show me a schematic of a simple disposable camera charging circuit? pls show the transistor number and type

Posted by buddybro 4 years ago


I just designed (if it works out) a super efficeint Beam Solar engine that works at low voltages. Before I post it I want to ask a few questions to see if I need to revise my design. 1) MOSFETs work on voltage, no current, right? 2) Do MOSFETs have a voltage drop, like biploar transistors have a voltage drop of about 0.6 volts? EDIT: I got a new design that I want you guys to evaluate that doesn't use mosfets. It's incredibly simple and I want to know what you guys think. How it Works: The solar cell energizes the transformer coil while turning on the transistor. The transistor shorts the circuit and then the transistor turns off, then it repeats creating pulsed dc that drives the stepup transformer. I chose this design because there's very little components and there's no voltage drop across the transistor to the transformer. Theoretically this could run on as low as 0.7 volts, which is good for BEAM robots.

Posted by guyfrom7up 10 years ago


Hi, I'm trying to build Ruby guitar amp for my brother, but my problem is that I can't find this MPF102 transistor or any of its equivalents where I live. and if I order it online it will cost me as much as a Marshall amp costs. I will appreciate any help or suggestions whether to replace the transistor or modifying the circuit.

Posted by soranblue 12 months ago

Supplying power to the PIC12F508 through a transistor.

I'm trying to supply power to a PIC12F508 via a transistor, so it can turn itself off once it has finished working to save power. The Idea is for the push button to supply power to the chip, which sets GPIO5 high on power up, so turns on the transistor, allowing power to continue flowing to the chip after the button is released. The PIC turns on correctly when the button is pressed, but will not remain on, despite power being supplied to the transistor from GPIO5. Another possible issue is that while the chip works properly, it continues to put a high on GPIO4, lighting the LED while VSS is disconnected. I have checked that the code functions correctly, and have tested this without the additional lines from the programmer. Any suggestions would be appreciated.

Posted by The Skinnerz 7 years ago

how to convert negative pulse to positive

Hello.. I built a transistor scr to turn on leds in my car from my remote.. my remote uses negative pulses to turn on and off... now the problem is that the scr needs a positive pulse to turn on but it uses negative to turn off,, so turning it off isn't a problem.. Im pretty sure I can just use a transistor to do this.. here is the schematic I used to build the scr...  ... fig 75b... is there a way to modify this circuit to make the turn-on negative or just a way to use another transistor to make my negative pulse positive? I could easily use an automotive relay to do this but im trying to make this as small as possible and its still on the breadboard.. I want to get this figured out before I put it on pcb.. thanks for your help

Posted by aclark32 4 years ago

Standardized Electronic Components?

Hello all, I was just wondering about finding electronic components. Some parts, like resistors and capacitors, seem pretty easy to sort out as long as you aren't looking for something out of the ordinary, just find the values you need rated for the wattage, etc. However, in the case of transistors and things like that, I am always seeing many different numbers (people say "a such-and-such transistor, like a {serial number}". Is there some general standardization for these parts? Or at least, some nearly universal sourcing that is considered a "standard"? I only wonder because trying to find components can be a real pain. I have a transistor, I know it's an NPN Darlington transistor, but that's about it. Others that I have salvaged I don't even know that much about. Any explanation or links to sites that explain these things would be much appreciated. Thanks in advance for any help!

Posted by victus_maestro 9 years ago