The above relation tells that the current available to drive the load is 100 times that of the input current of the transistor.Ĭonsider the below figure where NPN transistor is used to switch the lamp with variable resistor connected between the source and the base terminal. Load current = Current gain (β) × base current Transistor gain or Current gain (β) = load or collector current/ input or base current The current gain or beta of a transistor is the ratio of collector current to base current. Darlington TransistorīACK TO TOP Why We Use Darlington Transistor?Īs we know that to drive the transistor into the conduction mode a small base current is required, when the base is connected as input, emitter as common and collector as the output.īut, when we consider the load at the collector terminal, this small base current may not enough to drive the transistor into conduction. Let us look in brief about this transistor with applications. Many opto-isolator circuits are made with Darlington transistors to have high current capacity at the output stage. These transistors are found in different types of applications such as power regulators, motor controllers, audio amplifiers, etc. In today’s market, wide variety of Darlington transistors are available that are varied by polarity, collector current, power dissipation, package type, maximum CE voltage and so on. Darlington configuration was invented by Sidney Darlington in the year of 1953. Example of Darlington Transistor CircuitĪ Darlington transistor or simply Darlington pair is mainly used to offer a very high current gain even with low base current.Darlington Transistor or Darlington Pair.Used where high amplification is neededĢD dimensions will help you in placing this component at the time of making circuit on perf board or a PCB.Can be used to switch high current (upto 51) loads.Hence if you are looking for a NPN Darlington transistor with high collector continuous current and a good current gain, then this transistor might be the right choice for you. The only considerable drawback of this transistor is that the base voltage is high, it is around 1.5V Since it is a combination of two circuits it can also allows high current to pass through it (upto 1.2A) which makes it ideal for high current applications. Normal transistor have a current gain for around 100-300 but our Darlington transistor has a gain of 20000 hence it can be easily used in amplifier applications. The 2N5306 transistor is very much similar to the commonly used NPN transistors, but it is way more powerful than those since it is a Darlington transistor. Where to use 2N5306 Darlington Transistor? This is exactly where a Darlington transistor comes in. But in some application, the base current will be limited and cannot be increase during which we have to increase the transistor gain. So for loads consuming high power it becomes mandatory to increase the base current. Load current=i/p current X transistor gain As we know a transistor is turned on by providing an input current to the base pin (current controlled device) and when it turns on it allows the load current to flow through it which can be given by the formulae It decides how much times the load current can be amplified based on the input current to the bias pin. The current gain is an important property for a Darlington transistor. What is Current Gain? Why is it important? For example the transistor here has a current gain of 20000 and a collector continuous current of 1.2A because of its Darlington properties. One very important function of a transistor is its very high current gain. Yes the transistor you see above is actually a combination of two transistors provided in a single package to make it easy to use in our circuits. Out of which one transistor will be an NPN transistor and the other will be a PNP transistor. The Darlington Transistors are made up of two transistors combined togather.
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