What is a Darlington transistor

Modern electronics there thanks to the tireless work of the scientists who invent more and more electronic components, and these inventions often get the names of their creators. For example, a Schottky diode or a Zener diode (zener diode in common). So among these elements is a special Darlington transistor, here with him and I want to introduce you today. So, let's begin.

History of discovery

Darlington transistor (aka composite transistor) was first proposed engineer S. Darlington back in 1953. And at its core Darlington transistor - a cascade connection is usually two (much less three or more) of bipolar transistors. Moreover, they are connected so that the load chain in the emitter of the preceding stage is the base-emitter subsequent stage. The collectors of transistors are combined.

Also it turns out that the current flowing through the emitter of the first transistor is the base current of the second transistor.

So why build such a device? And here is why.

The main advantages of the build Darlington

Thus, the main and indisputable advantage of this assembly is the gain h21. So if we look, for example, a transistor 6GV7 (Aka KT816), Then he gain h21 equal min 25, max 275, While KT973A active factor is h21 min 750, Max 5000.

As you can see the difference is enormous. Besides such transistors can be operated at relatively high voltages. But where there are the advantages and disadvantages.

Cons Darlington transistors

As with any device composite transistor has its shortcomings and, perhaps, the most significant disadvantage is the low speed of assembly, especially at the transition from the open state to the Closed.

It is for this reason that such assemblies are used in low-frequency key and amplifying circuits.

Just forward voltage composite transistor Darlington is almost two times more than the average.

And equal to the sum of the voltage drops on P-N transitions connected transistors. This in turn leads to the fact that during the flow of current through the transistors assembly dissipate more power, and hence requires better cooling.

Just a suspended minus is the fact that these transistors on circuit diagrams are identified in the same way as regular transistors.

Assembly Darlington found the widest application in electronics. For example, they are used extensively in IC ULN2003A and so on. n., who so love to use many hams.

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