![]() We investigate temperature-based and optical field-based control strategies of the Darlington pair in terms of both steady-state and transient thermal flow characteristics through numerical simulations. We refine previous models to incorporate these transistor-transistor interactions and introduce an intermediate thermal bath to facilitate the thermal energy exchange between the Darlington pair transistors. Unlike previously studied models, multitransistor configurations like this contain internal transistor interconnections whose temperatures cannot be biased externally but are determined by the individual transistors' internal dynamics. We create the electronic Darlington pair's thermal equivalent using two individual thermal transistors in a similar configuration. In electronics literature, the Darlington pair is a two-transistor configuration commonly used to construct electronic amplifiers with higher gain than is possible with a single transistor. With several models for individual thermal transistors already developed, the next natural step is to investigate how multiple thermal transistors can interconnect to build useful composite devices. ©Kitronik Ltd – You may print this page & link to it, but must not copy the page or part thereof without Kitronik's prior written consent.Recent progress in manipulating individual quantum systems has led to the development of quantum thermal transistors, which control the thermal conductivity between two of its terminals according to an input signal on its third terminal. We hate spam too and promise to never sell or share your email address, and you can unsubscribe at any time. We have two electronic kits which utilise a Darlington pair to allow an output current of up to half an Amp to be controlled:ĭownload a pdf version of this page here Learn more about the author read more » If you found this article helpful and you would like to receive product updates and free electronic resources from us then sign up to our newsletter here. The Interactive Learn & Test Zone, a place to learn about and test yourself on electronics.You may be interested in other similar resources: This article is listed in the resource section of the web site within the understanding electronics section. It is also worth noting that the voltage drop across collector and emitter pins of the Darlington Pair when the turn on will be around 0.9V Therefore if the supply voltage is 5V (as above) the voltage across the load will be will be around 4.1V (5V – 0.9V) Therefore the base voltage will need to be greater than 0.7V x 2 = 1.4V. As two transistors are used in a Darlington Pair this value is doubled. Normally to turn on a transistor the base input voltage of the transistor will need to be greater than 0.7V. Therefore this will allow a very low input current to switch a much bigger load current. 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 that this gives a vastly increased current gain when compared to a single transistor. This can be achieved by using a Darlington Pair. If it is not possible to increase the input current then the gain of the transistor will need to be increased. As stated earlier this equals the input current x the gain of the transistor (hFE). This may mean that a single transistor may not be able to pass sufficient current required by the load. In some applications the amount of input current available to switch on a transistor is very low. This would mean that the current available to drive the load would be 100 times larger than the input to the transistor. For a normal transistor this would typically be about 100. The amount of current that can pass through the load in the circuit above when the transistor is turned on is: Load current = input current x transistor gain (hFE) The current gain varies for different transistors and can be looked up in the data sheet for the device. Transistors have a characteristic called current gain. The Darlington Pair can be made from two transistors as shown in the diagram or Darlington Pair transistors are available where the two transistors are contained within the same package. This mean that a tiny amount of current from a sensor, micro-controller or similar can be used to drive a larger load. A Darlington pair is two transistors that act as a single transistor but with a much higher current gain.
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