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transistor

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Nigel Goodwin

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Buy/build one of the cheap component testers from China, they identify what component it is, and tell you the pin connections - EXTREMELY useful items to have, and ridiculously cheap (I think I've built four now?, or is it five?).
 

ronsimpson

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how to identify base ,emitter and collector of any transistor
With a simple ohm meter you can test for a diode. (use diode test if the meter has one)
The base has two diodes. B-E and B-C.
It is not easy to find C or E if you only have a simple meter.
Some meters have a "transistor test" function. If you have the base right, the transistor will have gain or no gain if the CE is right or wrong. (you will have to guess NPN or PNP)
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Many transistors have the same pinout (for a given package).
Can you attach a picture of your transistor?
 

Nigel Goodwin

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Grossel

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I would recomend read it's datasheet.

But ifthe component doesn't have a clear code of type, you can't know for sure it is actually a transistor. It might as well be a voltage source (like the 7805), or it may actually be a darlington pair with resistors (I remember some old japanese vhs players had many of those) that I doubt that a cheap transistor tester till recognise properly.
 

Nigel Goodwin

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I would recomend read it's datasheet.

But if the component doesn't have a clear code of type, you can't know for sure it is actually a transistor. It might as well be a voltage source (like the 7805), or it may actually be a darlington pair with resistors (I remember some old japanese vhs players had many of those) that I doubt that a cheap transistor tester till recognise properly.
The cheap AVR based component testers are really absolutely amazing, they certainly recognise darlingtons, no idea about ones with resistors in though - although I would imagine so, as they still give high gain just as a non resistor one does.

They don't detect voltage regulators though, as they obviously require higher voltages so wouldn't be worth adding.

But it's worth sticking ANYTHING you don't know across one, and see what it says - like my counterfeit LM35's tested as SCR's and some as transistors. When I got some real ones I checked those, they all tested as 'transistors' but with very low gain.

For anyone who is interested, you can get the full design details from a website, presumably from the original designer?, where he explains the numerous different tests that are done to try and decide what a component might be. I imagine all the cheap Chinese kits are based on variants of his original work?.
 

unclejed613

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you can identify the base, as well as the polarity by doing measurements (with a DMM in "diode check" mode). one lead will act as the "common" of what seems to be two diodes, and that's the base lead. reverse bias applied to the two "diodes" can identify the emitter, as one of them will act as a zener diode between 5 and 8 volts (this test should be done with a current limit of about 1 milliamp).

some common pinouts:
TO92 transistors
part number begins with 2N usually EBC across the front
part number begins with 2S (or just an A, B, C, or D) usually ECB across the front
part number begins with BA, BC, BD (i'm not as familiar with european types) CBE seems to be common

TO3P, TO264
most of these are all BCE

TO126, TO220
most of these are BCE

TO202
most of these are EBC

the main reason TO3P, TO264, TO126, and TO220 are BCE is that they are derived from the TO3 and TO66 packages, and in many situations can use the original TO3 or TO66 sockets without much trouble.


these pinouts are the most common pinouts, but there ARE exceptions (that's part of what keeps this business interesting)
 
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