In an age with so many digital devices, professionals who can fix them correctly and quickly are worth their weight in gold. But eliminating the faulty element and soldering a new one is only half the battle, the most important process is troubleshooting. And in order to understand the scheme, you need to know the principle of operation of each of its elements.
What is a Darlington transistor
The Darlington transistor does not exist as a separate element. This name was given to the assembly in a certain sequence of two transistors in order to increase the current gain. The first transistor carries the current-carrying function, and the second simply controls the first. Similarly, a small relay can handle large loads. This electronic circuit is also called "Darlington steam" and is widely used in modern electronic devices.
Principle of operation
Amplification is not the only characteristic of the Darlington transistor, it is also used in circuits as a switch.
The sequence of processes in the transistor in the switch mode (for example, an NPN element is used):
- Condition: grounded transistor base and no current from emitter to collector.
- The element is switched to the "Off" mode.
- With a base bias of more than 0.7 V, a current appears that flows through the emitter to the collector.
- The transistor goes into the "Enable" mode.
The Darlington transistor is available in both NPN and PNP versions. Also, the element is manufactured with different voltage ratings.
Where are Darlington transistors used
Darlington transistors are widely used in DC motor control circuits and relays. They are also used to turn off and on individual circuit elements, such as lamps. These electronic elements are popular because of their sensitivity to even a small input current, which allows you to create accurate and high-quality circuits.
Darlington arrays are used to control high-power motors, lamps or electromagnets, which not only work safely with inductive loads, but also consume a small amount energy. But such control cannot be provided only by an array - the circuit also uses elements on a microprocessor base.
The main disadvantage of the Darlington transistor
The main drawback of the element is its excessive heating. The increase in temperature occurs due to the bundle of two transistors, respectively, there is a double voltage drop at the base emitter - 1.2 V, instead of 0.6 V, which leads to an increase in current. More current in an element means more heating.
But the problem of excessive heating can be solved: in order to prevent a sharp increase in temperature, it is necessary to assemble a transistor pair according to the Shiklai scheme. This scheme involves the use of both NPN and PNP junctions. The main advantage of such a circuit is that 0.6 V is enough to turn it on, and not 1.2 V as in a Darlington transistor.