Hello, friends!
Simple question:
So anyone know integral darlington transistor. Can i build it from discreet elements?
For example i want to use in darlington pair somthing like: BC8xx - general BJT and low saturation BJT(can handle up to 3A in sot23-3 case, bet have quite low Hfe)?
Yes, but when BJT is on the same waffer, their parameter are quite nice matched. But discreet element parameters, aren't matched? Can it have some negative effects?
yes indeed. but it will be called a darlington pair. a darlington transistor is a single discreet transistor which internally has two transistors connected in a darlington configuration
You can connect two transistors in different Darlington pairs. It can be connection of PNP+PNP or NPN+NPN or NPN+PNP or PNP+NPN. Second transistor has usually higher current ratings if needed.
But darlington transistors can have much higher collector current than darlington pairs,because it's collector current limit by single transistor.Such as bc557,it can only provide 100ma current of collector.Can it be much useful?
The hand-built darlington configuration also has
higher collector current tolerance than a single transistor... I would recommend getting the
integrated one, though since they will probably yet higher tolerance due to process optimizations, plus
they usually come with a built in heat spreader,
which
you might need...
To imprve properties of a darlington transistor it is goo idea to include base-emitter resistors: for first transistor in the range of 5-20kΩ, for power transistor 100-1kΩ.