Darlington tube

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Darlington tube

  The Darlington tube is the two triodes connected together, the polarity only recognizes the front triode. The specific connection method is as follows. Take two transistors of the same polarity as an example. The front triode collector is connected to the rear triode collector, and the front triode emitter is connected to the rear triode base. The front triode power is generally smaller than the rear triode. The triode base is extremely Darlington's base pole, and the rear triode emits an extremely Darlington tube emitter. The usage is the same as the triode, and the amplification factor is the product of the amplification of the two transistors.

Darlington principle

The Darlington tube is also known as the composite tube. He connected the two triodes in series to form an equivalent new triode. The magnification of this equivalent transistor is the product of the original two, so it is characterized by a very high magnification. Darlington's role is generally to amplify very small signals, such as high-power switching circuits, in highly sensitive amplifier circuits. In electronic circuit design, Darlington connection is often used in power amplifiers and regulated power supplies.

Composite pipe composition principle [1]

At the correct applied voltage, each transistor operates in the amplification region.

The collector current or the emitter current of the first element serves as the base current of the second element, and the true current direction is uniform.

The type of equivalent transistor is the type of the first original.

Darlington circuit has four connections: NPN + NPN, PNP + PNP, NPN + PNP, PNP + NPN

The first two are the same polarity connection, and the latter two are heteropolar connections. The same polarity connection of NPN+NPN: B1 is B, C1C2 is C, E1B2 is connected together, then E2 is E. Here also talk about the heteropolar connection. Take NPN + PNP as an example. Let the three poles of the former transistor T1 be C1B1E1, and the three poles of the latter transistor T2 be C2B2E2. The connection of the Darlington tube should be: C1B2 should be connected together, and E1C2 should be connected together. The pin of the equivalent transistor CBE, C=E2, B=B1, E=E1 (ie C2). The equivalent triode polarity is the same as the previous triode. It is the NPN type.