PLEASE HELP, I am using BC638 transistor as a switch for driving 7 leds
connected in parallel, since i'm pulsing the leds so i require a high current around
70-75 mA for each led, for 7 leds it comes to around 500mA and as BC 638
can source that much current but i'm unable to sort out the pinouts for the
transistor as thedatasheet says
1- emitter, 2-collector(middle leg as cpllector) and 3 -base(bottom view)
but my testintg says middle leg is the base

can any one help me in telling the correct pinout for the transistor
OR can any one tell me which other transistor i can use for the same
purpose.
I would be greatful for any help you could give.
thanks

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hello

 

Trust the datasheet - just make sure you are looking at exactly the right datasheet and case type.

I agree - looking at the flat face, from left to right, it is emitter, collector, base.

How are you testing it?

 

i am testing the two p-n junctions and since currnt flows from p 2 n
so the pin that is common for the two 700ohms reading will be the
base (thats purely a rough idea i have collected from what knowledge i have about electronics and transistors)
and bc638 is a pnp transistro so n will be the base
so by my test middle pin is n so its the base

i have the datasheet from kec and fairchild

am i correct with my testing.

regards

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hello

 

hi econsyst,

when you say pnp or npn, it does not follow that the middle pin is always the base, there are transistors that conform to that. these transistors have this pin placement assuming the flat side is facing you, EBC - ECB - BCE & CBE.

since you have the datasheet again assuming you have the correct datasheet, then follow their pin configuration.

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\"NONE BUT THE BRAVE DESERVES THE FAIR\" ~Shakespeare~