Transistors are very useful, they are the building blocks of modern systems. For example a modern computer CPU will contain over a billion transistors. Please subscribe and like my Facebook page at: / powertraceelectronics
*Summary of how to identify if a transistor is NPN or PNP:* PNP: base is negative. NPN: base is positive. *EDIT: An easier way to remember!* PNP: Positive-Negative-Positive NPN: Negative-Positive-Negative
Fine tip. Thank you friend. Briefly the 2 outer legs are either P's(+ve) or N's(negative). So if you test them with their proper polarity by the Meter they should give the same readings as in the beautiful Video here.
It may show up as a PNP with the diode test, but unless you know for sure that the TO-92 package is standard, the collector and emitter could be interchanged. Looking up the number may be necessary to confirm which is which.
Thank you for your explanation of how to figure which was which. It helped me greatly once I turned my Multimeter from Resistance to Diode. (It's the same setting on the selector, I just needed to press the Alt Function button). Taken me 10 minutes to notice that booboo.
Hey, good tutorial. Sorry, dont do social media. Will do similar experiment with pre determined transistors, NPN, PNP, 2N3904(npn), and, 2N3906(pnp). From what I have learned, can sort out salvaged transistors without data sheet. Thanks, C.
I have a question. Please help me with this. My machine works on pnp sensor but due to some problem the sensor got damage now at the current time I dont have a pnp sensor but a npn sensor. Can I use npn in place of pnp using a relay if yes please let me know how to do the wiring
You rock man! I always take the time to look up the serial number of each transistor which is time consuming. This is much quicker! I appreciate your information. Take care!
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It does matter yes, normally the forward drop between the base and emitter is slightly greater than the base to collector due to the slightly higher doping of the base to emitter junction, so you can find out which the collector and emitter are by knowing this.
emitter is also to the right on both transistors as was tested. emitter is always a little higher out of circuit. great job keep up the good work and the base is not always in the middle. what determines that is where it was made. japan Europe usa etc. 73 kf4gyp Ray
npn base positive emitter/collector negative should read 0.7 volts reverse the leads should be open transistor is good, pnp base negative with respect to emitter /collector 0.7 volts reverse leads should give open ,if any of the tests should read low or 0 volts drops the transistor is knackered.
+Charles W Harris Jr Not all BJTs have the Base lead in the middle on the package. They only have to be internally connected to it. Depending on how the manufacturer makes and assembles the transistor casing determines which external lead is which.
+Kenneth Waggoner I think for all BJT transistors, the base MUST be in the middle. I mean, the BJT transistor basically works because the base is in the middle otherwise, it wouldn't do what it does!
