*I will only add that the transistors of the same name in different designs can have different pinouts. Always check!
So what view is that? Sometimes the datasheet gives top view, sometimes bottom view. 180deg different. Watch out for those gotcha's!
Jan
Jan
Yes I can see that. I mean the view of the device. Top view, bottom view.
Like in the attached example. Those differ per manu and data sheet. It's a mess and you need to check, recheck, double check.
It's a good idea to make such a list but ideally it should have the image of the device next to the pinout so you know the orientation.
Jan
Like in the attached example. Those differ per manu and data sheet. It's a mess and you need to check, recheck, double check.
It's a good idea to make such a list but ideally it should have the image of the device next to the pinout so you know the orientation.
Jan
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Funny thing is, in Jan´s attached example "physical pin order is the same on both" and you can insert any in the same PCB hole array, BUT the "assigned" numbers "1 - 2 - 3" are in reverse.
Meaning *just* stating "1 - 2 - 3" is not enough.
Agree that a "package/case" view is needed.
When I use transistors like those, I make it a point to check the transistors' pinout immediately before I solder them in place. I also avoid to manipulate a transistors layout mentally, as with age, spatial ability is greatly diminished, at least, it happened with me.
Like an idiot, use a humble pencil and paper: it will save you unnecessary headaches.
Like an idiot, use a humble pencil and paper: it will save you unnecessary headaches.
you are right i have had some of the same type where the pin out was different, i should have mentioned it
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ones a 550 the other 559, so they are different not in reverse, but you are right
i always check whats fitted against whats specified and what the board actualy is, it just saves a bit of time going back and forth when you are sure what is fitted etc and it is usefull to have in front of you when testing, well i found it usefull anyway.
I just use the hFE test on a regular DMM. Reverse beta is almost always much lower.
European 2N’s can often go CBE instead of EBC, but not always. Definitely have to check EU 2N’s. Fairchild KSA/KSC can be ordered in both EBC and ECB, with slight differences to the full part number. And I’ve seen a couple instances where Mouser’s stock number is for ECB version according to the data sheet, but you get EBC. I mark it on the parts drawer when they go into my stock.
European 2N’s can often go CBE instead of EBC, but not always. Definitely have to check EU 2N’s. Fairchild KSA/KSC can be ordered in both EBC and ECB, with slight differences to the full part number. And I’ve seen a couple instances where Mouser’s stock number is for ECB version according to the data sheet, but you get EBC. I mark it on the parts drawer when they go into my stock.
looks like a great tool, trouble is i dont want to take anything out of circuit unless i realy have to as you risk unessesary damage, so i just want something in front of me as a guide while testing
The green screened device posted by Mark Johnson above, inevitably causes one's logic wetware, to ponder about the way it can decide for itself what a transistor's three pins are. If an algorithm designed for a microprocessor can do it, it can be done in other ways more accessible to human beings.
How is it done?
One way is the BJT diode test. This can find the base with certainty, but the emitter and collector give the same result, hence they are not distinguishible. Another way that springs to mind, is to use the avalanche voltage for the junctions, but feeding current through a very low current very high impedance current source. The junction which gives about 5V should be the base-emitter junction.
How is it done?
One way is the BJT diode test. This can find the base with certainty, but the emitter and collector give the same result, hence they are not distinguishible. Another way that springs to mind, is to use the avalanche voltage for the junctions, but feeding current through a very low current very high impedance current source. The junction which gives about 5V should be the base-emitter junction.
That.
Same here, raw diode test can be inconclusive, since you have TWO diodes inside, pointing towards/away from Base, BUT although reversed transistor does work reversed, Hfe is abysmal.
Forward it´s what´s expected, say 200 to 500; reversed it´s about 10X smaller, say 30 to 50.
Agree that measuring Vbe "zenering" is also accurate, but requires a little more "hardware".
Old enough to remember when Zeners were fancy expensive parts, and it was *common* to use a reverse biased transistor as reference.
Oh well, miss those dinosaur steak BBQs 🙁
With a 5V DC power supply, a 1μA can be obtained using a resistance of 5MΩ or approximately using a 4.7MΩ. This can be applied to the base while the transistor is connected in common emitter mode. The current through the collector would need a milliammeter of a few milliamps.
This arrangement can work for all those who do not have a multimeter which can measure Hfe. With a base current of 1μA, the collector current would be between 200μA and 500μA. Be aware there are transistors which have higher or lower Hfe.
In my case, I look up the transistor's datasheet when this is available.
This arrangement can work for all those who do not have a multimeter which can measure Hfe. With a base current of 1μA, the collector current would be between 200μA and 500μA. Be aware there are transistors which have higher or lower Hfe.
In my case, I look up the transistor's datasheet when this is available.
That little green thingy does wonders, I use it mostly for hFE matching. It helps a lot when in doubt and can also discriminate between bjt/fet and detect polarities when markings have faded away.