This process can be done by using a Darlington pair.Ī Darlington transistor contains two transistors, but it acts as a single transistor with a current gain that equals. If the input current increase is not possible, then the gain of the transistor will need to be increased. So, the load current is equal to the i/p current and the gain of the transistor. So, a particular transistor cannot supply ample current to the load. The amount of i/p current to switch on a transistor is low in certain applications. So the current available to drive the load is 100 times greater than the i/p of the transistor. For a normal transistor the current gain would be normally around 100. The current gain of every transistor varies. Load current=i/p current X transistor gain When the Darlington transistor is switched ON, then the current supplies through the load to the circuit Working of a Darlington Pair Transistor What is Current Gain?Ĭurrent gain is the most important characteristic of a transistor and it is indicated with hFE. The below Darlington circuit is built with two transistors shown in the circuit diagram. For instance, the following circuit is explained below. PNP and NPN Darlington Transistors Working of a Darlington TransistorĪ 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 max CE voltage of Darlington transistor is 450V and power dissipation can be in the range of 200mW to 250mW. The common values of max CE voltage are 30V, 60V, 80V & 100V. Darlington transistors are classified into different types by Power Dissipation, Max CE Voltage, Polarity, Min DC Current Gain and Type of Packaging. So, the i/p transistor amplifies the current even further amplifies by the o/p transistor. In this transistor, the emitter of the i/p transistor is connected to the o/p of the base of the transistor and the collectors of the transistor are wired together. This transistor is also called as a Darlington pair, contains of two BJTs that are connected to deliver a high current gain from a low base current. 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.Darlington Transistor Darlington Transistor.Can be used to switch high current (upto 5A) loads.So, if you looking for a transistor that could be easily controlled by a Logic device to switch high power loads or to amplify high current then this Transistor might be an ideal choice for your application. Although care has to be taken to check if the logic device can source upto 120mA. This transistor has a low Base-Emitter Voltage of only 5V hence can be easily controlled by a Logic device like microcontrollers. TIP120 transistor is known for its high current gain (hfe = 1000) and high collector current (IC =5A) hence it is normally used to control loads with high current or in applications where high amplification is required. This increases the current gain and current rating of this transistor. The Darlington pair inside this transistor is shown clearly as its internal circuit schematic belowĪs you can see, there are two transistors inside this TO-220 package in which the emitter of first transistor is connected with the base of second transistor and the collector of both transistors are connected together to form a Darlington pair. If you need more voltage then you can check other transistor in the same family lit the TIP122. It can also withstand about 60V across its collector- Emitter hence can be used to drive heavy loads. It functions like a normal NPN transistor, but since it has a Darlington pair inside it has good collector current rating of about 5A and a gain of about 1000. The TIP122 is a Darlington pair NPN transistor. Note: Complete Technical Details can be found at the TIP120 datasheet given at the end of this page. Continuous Collector current (IC) is 5A.High DC Current Gain (hFE), typically 1000.This makes it suitable for medium and high power electronics like controlling motors, solenoids or high power LEDs.Ĭontrols the biasing of transistor, Used to turn ON or OFF the transistorĬurrent flows in through collector, normally connected to loadĬurrent Drains out through emitter, normally connected to ground It can switch loads upto 60V with a peak current of 8A and continuous current of 5A. The TIP120 is a NPN Darlington Power Transistor.
0 Comments
Leave a Reply. |