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How does a Darlington transistor work?
A Darlington Pair acts as one transistor but with a current gain that equals: Total current gain (hFE total) = current gain of transistor 1 (hFE t1) x current gain of transistor 2 (hFE t2) So for example if you had two transistors with a current gain (hFE) = 100: (hFE total) = 100 x 100 (hFE total) = 10,000 You can see …
What is the disadvantage of Darlington pair transistor?
Drawbacks or disadvantages of Darlington transistor ➨Bandwidth is limited. ➨This configuration introduces phase shift at certain frequencies in negative feedback circuit. ➨It offers high power dissipation due to high saturation voltage. Hence overall leakage current of Darlington pair is higher.
When the transistor is in saturation mode?
Saturation is the on mode of a transistor. A transistor in saturation mode acts like a short circuit between collector and emitter. In saturation mode both of the “diodes” in the transistor are forward biased. That means VBE must be greater than 0, and so must VBC.
What is the collector current of a Darlington transistor?
Darlington Transistor Circuit The collector current is equal to the load current, IC = 80/12 = 6.67 A Darlington transistor output current is given as Ic = IB (β1 + β2 + β1 β2),
Why is the leakage current high in the Darlington pair?
The overall leakage current is high because the leakage current of the first transistor is amplified by the next transistor. That’s why the three or more stages of Darlington is impossible. Hence, the Darlington pair is very useful in most of the application because it provides high current gain at low base currents.
How does a 100K ohm resistor work on a Darlington pair?
A 100k ohm resistor acts as a protective resistor for the pair of transistors. When the switch is closed, a specified voltage greater than 1.4V is applied across the Darlington transistor. This causes the Darlington pair to become active and drives the current through the load.
How is the current gain of a second transistor determined?
Therefore, the emitter current of the second transistor is very large which is high enough to drive high loads. Suppose if the current gain of the first transistor is β1 and the current gain of next transistor is β2, then the overall current gain of transistors will be the product of β1 and β2.