truf Posted August 23, 2006 Report Share Posted August 23, 2006 Hey,I want to know if there is a way to find out which pin on a transistor is the collecter, and which is the emitter. I know that a transistor is basically 2 diodes, so finding the base is easy. Thanks very much! Quote Link to comment Share on other sites More sharing options...
gogo2520 Posted August 24, 2006 Report Share Posted August 24, 2006 Hi truf Try finding the data sheet that should tell you or tell us what the part number of the transistor is so we can help you. have fun gogo Quote Link to comment Share on other sites More sharing options...
Theatronics Posted August 24, 2006 Report Share Posted August 24, 2006 It is kind of tricky.The problem is that the test it's self could destroy the device dependingon it's design. One method is to compare the breakdown voltages ofthe E to B diode VS. the C to B diode. I would have to break out my theorybooks but I suspect (based on the physical model most NPN/PNP devices usethat the C to B diode will go into a ziner behaviour at a voltage lower than theE to B diode. THe problem is that if you are trying to test a darlington, or a JFETor any other type device you will end up getting no where at best. (You might end up in a smoke filled room at worst)If you can read the part number off the part then looking up the datasheet is the best method.If you can't find the datasheet, Post the numbers here and someone will gladly post your answer.When all else fails. Build a very low current circuit (High Ohm resistors) and Guess.If the device doesn't work one way, flip it around and try another way.-Mike Quote Link to comment Share on other sites More sharing options...
truf Posted August 24, 2006 Author Report Share Posted August 24, 2006 I mean like the NPN/PNP transistors. Mostly the ones that start with 2N, MPS, and BC.Thanks Quote Link to comment Share on other sites More sharing options...
Theatronics Posted August 24, 2006 Report Share Posted August 24, 2006 Well, Heres a sample of the pinouts. Quote Link to comment Share on other sites More sharing options...
Theatronics Posted August 24, 2006 Report Share Posted August 24, 2006 thats what I said.IF you reverse bias test the transistors, the COllector to base will be LOWERthan the Emitter Base. But the test COULD destroy some diodes.SHesh, I not wrong ALL the time.-Mike Quote Link to comment Share on other sites More sharing options...
walid Posted August 24, 2006 Report Share Posted August 24, 2006 I understand his question in another waymay be he ask like thisif he has a transistor on the table and he wand to identify its terminals and typeuse your digital multimeter diode function, first assume your trans is npn type, then put the red wire in one leg and the black on another leg .... repeat this untill you have a reading with the red on one lege and the black one time on the 2nd and then on the 3dthen the leg in contact with red is base and the others are C and E the bigger reading is E and the smaller is Cif u can't get any reading then assume it is pnp and repeat the above with the black first to one leg assumed base....may be u hardly understand me but i want to helpthanks Quote Link to comment Share on other sites More sharing options...
truf Posted August 24, 2006 Author Report Share Posted August 24, 2006 Thanks very much! Especially to Walid! ;) Quote Link to comment Share on other sites More sharing options...
truf Posted August 24, 2006 Author Report Share Posted August 24, 2006 Hi again Walid,About how to find the Emitter and Collecter, when I used the diode function on an NPN transistor, I found out that the test worked, but the collecter and the Emitter only had a difference of about .004 V. Is this suppose to be that small?The B-C had about .654V and the B-E had about .657V.Thanks Quote Link to comment Share on other sites More sharing options...
walid Posted August 24, 2006 Report Share Posted August 24, 2006 yes it is very small like thatI'm pleasure, it is the first time i can help a friend in this great communitygood luck trufalways I get all my project's parts from my old junk so i check them especially the transistors, you can say that i check more than 5000 transistors in that way and always the difference be that small. Quote Link to comment Share on other sites More sharing options...
audioguru Posted August 24, 2006 Report Share Posted August 24, 2006 thats what I said.No you didn't.IF you reverse bias test the transistors, the Collector to base will be LOWERthan the Emitter Base.No it isn't.The collector-base is almost always reversed-biased in circuits and has a high breakdown voltage.For a 2N3904 it is 60V. The emitter-base is not usually reverse-biased in circuits and has a max rating of only 6V for a 2N3904.SHesh, I not wrong ALL the time.Hee, hee. ;DNo, just most of the time! ;D Quote Link to comment Share on other sites More sharing options...
audioguru Posted August 24, 2006 Report Share Posted August 24, 2006 About how to find the Emitter and Collecter, when I used the diode function on an NPN Quote Link to comment Share on other sites More sharing options...
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