how to know the transistor is npn or pnp

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newone
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how to know the transistor is npn or pnp

how to know the transistor is npn or pnp

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HighFrequency
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Re: how to know the transistor is npn or pnp

ummm... read the part number off the transistor case, then google it.
There is only one correct answer, mine.

mnboy
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Re: how to know the transistor is npn or pnp

Either Google it, or do a diode test.

jollyrgr
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Re: how to know the transistor is npn or pnp

This can be done rather simply with an Ohm meter. If the leads are labeled, you have most of the problem solved. If not, all is not lost. With standard TO-92 case devices with the flat side facing you and the leads pointed down, the pin out is E B C in most cases. But in rare cases this may not be the proper pin out. In addition to explaining the procedure for testing for the polarity, I'll explain how to find which lead is what.

Mentally identify the leads as 1, 2, and 3. Take your Ohm meter and measure the resistance between leads 1 and 2. (Use the "diode" setting or the range that will give you 200 or so Ohms on the max scale.) Reverse the meter leads and note the reading again. Do the same for leads 1 and 3, measuring with both polarities of the meter. Lastly do the same measurements on leads 2 and 3.

If you are familiar with transistors you will know the bipolar style are NPN or PNP The BASE is the material that is in the "center" letter of the two types. Connect the RED meter lead to the BASE. Connect the BLACK meter lead to each of the other two terminals. If you get LOW readings on both leads this is an NPN transistor. If you get HIGH readings on both leads, reverse the meter connections and try again. This time if you get two LOW readings you have an PNP transistor.

To identify which lead is the EMITTER, take note of the two LOW readings. One of the two LOW readings will be just a bit lower than the other. The LOWER of the two low readings is the EMITTER lead. This is because the EMITTER is slightly more doped than the COLLECTOR. The EMITTER section is slightly larger as well as it must carry the BASE current in addition to the COLLECTOR EMITTER current.

(I hope I got this right and didn't mess up my polarity logic. Any faults or corrections are welcome.)
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Enzo
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Re: how to know the transistor is npn or pnp

EBC is for American transistors. Japanese numbers like 2SC945 have an E C B arrangement. Frankly I see more of them than I do 2N or MPS numbers. And I have never been sure which way Euro transistors are laid out.

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