Behavior
A Darlington pair behaves like a single transistor with a high current gain (approximately the product of the gains of the two transistors). In fact, integrated devices have three leads (B, C and E), broadly equivalent to those of a standard transistor.
Darlington pair of transistor is also called as super-beta transistor. Since it has the capacity to amplify the current output many a times a normal transistor configuration.
A general relation between the compound current gain and the individual gains is given by:
If β1 and β2 are high enough (hundreds), this relation can be approximated with:
Darlington pairs are available as integrated packages or can be made from two discrete transistors; Q1 (the left-hand transistor in the diagram) can be a low power type, but normally Q2 (on the right) will need to be high power. The maximum collector current IC(max) of the pair is that of Q2. A typical integrated power device is the 2N6282, which includes a switch-off resistor and has a current gain of 2400 at IC=10A.
A Darlington pair can be sensitive enough to respond to the current passed by skin contact even at safe voltages. Thus it can form the input stage of a touch-sensitive switch.
A typical modern device has a current gain of 1000 or more, so that only a small base current is needed to make the pair switch on. However, this high current gain comes with several drawbacks.
The basic Darlington transistor circuit is formed by taking the emitter of the input transistor and connecting it such that its emitter drives the base of the second and then connecting both collectors together
Read more about this topic: Darlington Transistor
Famous quotes containing the word behavior:
“A method of child-rearing is not—or should not be—a whim, a fashion or a shibboleth. It should derive from an understanding of the developing child, of his physical and mental equipment at any given stage, and, therefore, his readiness at any given stage to adapt, to learn, to regulate his behavior according to parental expectations.”
—Selma H. Fraiberg (20th century)
“Growing up human is uniquely a matter of social relations rather than biology. What we learn from connections within the family takes the place of instincts that program the behavior of animals; which raises the question, how good are these connections?”
—Elizabeth Janeway (b. 1913)
“If you are willing to inconvenience yourself in the name of discipline, the battle is half over. Leave Grandma’s early if the children are acting impossible. Depart the ballpark in the sixth inning if you’ve warned the kids and their behavior is still poor. If we do something like this once, our kids will remember it for a long time.”
—Fred G. Gosman (20th century)