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What is NPN Darlington transistor?

What is NPN Darlington transistor?

A Darlington Transistor configuration, also known as a “Darlington pair” or “super-alpha circuit”, consist of two NPN or PNP transistors connected together so that the emitter current of the first transistor TR1 becomes the base current of the second transistor TR2.

How do you test a Darlington NPN transistor?

How to Test Darlington Transistors

  1. Identify the base, collector and emitter leads on the Darlington transistor.
  2. Turn the multimeter dial to the diode setting.
  3. Clip or press the positive meter lead to the base lead.
  4. Touch the negative test probe to the collector and then the emitter.

How do Darlington transistors work?

A Darlington transistor acts as a single transistor with high current gain, it means that a small amount of current is used from a microcontroller or a sensor to run a larger load. The below Darlington circuit is built with two transistors shown in the circuit diagram.

Can you test a transistor in circuit?

Testing the transistor. Remove the transistor from the circuit for accurate test results. Hook the positive lead from the multimeter to the to the BASE (B) of the transistor. For an good NPN transistor, the meter should show a voltage drop between 0.45V and 0.9V.

What is a Darlington pair used for?

The Darlington transistor pair is a very useful circuit in many applications. It provides a high level of current gain which can be used in many power applications. Although the Darlington pair has some limitations, it is nevertheless used in many areas, especially where high frequency response in not needed.

What are Darlington transistors used for?

Applications of Darlington Transistor Darlington transistors are mainly used in switching and amplification applications for delivering a very high DC current gain. Some of the key applications are high and low side switches, sensor amplifiers and audio amplifiers.

How does the NPN configuration of Darlington transistor work?

Consider the NPN configuration of Darlington transistor. In this a very small base current causes a large emitter current to flow which is then applied to the base of the next transistor. Amplified current in the first transistor is again amplified by the current gain of the second transistor.

What kind of transistors are used in Darlington?

We can see NPN Darlington consist two NPN transistors, and PNP Darlington consist two PNP transistors. The first transistor’s emitter is directly connected across the base of other transistor, also the collector of the two transistors are connected together. This configuration is used for both NPN and PNP Darlington transistors.

What’s the difference between PNP and NPN transistors?

There is no much difference in the circuit using NPN or PNP. Below figure shows a simple sensor circuit which gives an alarm with the functioning of Darlington pair. This circuit is a simple water level indicator wherein Darlington pair is used as a switch.

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.

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