How does a Darlington transistor work as a switch?

How does a Darlington transistor work as a switch?

Darlington Transistors simply contain two individual bipolar NPN or PNP type transistors connected together so that the current gain of the first transistor is multiplied with that of the current gain of the second transistor to produce a device which acts like a single transistor with a very high current gain for a much smaller Base current.

How do you use a transistor as a switch?

To use a transistor as a switch, all you have to do is increase the current at the base terminal to a certain level, and the transistor will go into a state commonly known as “saturation.”

What does beta mean on a transistor switch?

Beta — also known as DC current gain — is a ratio relating to how much current gain you can expect through a transistor’s collector terminal given a certain amount of current going into the base terminal. In other words, the base current controls the collector current.

What’s the difference between a transistor and a NPN switch?

The equations for calculating the Base resistance, Collector current and voltages are exactly the same as for the previous NPN transistor switch. The difference this time is that we are switching power with a PNP transistor (sourcing current) instead of switching ground with an NPN transistor (sinking current).

How is a transistor arranged as a switc H?

If the circuit uses the BJT transistor as a switc h, then the biasing of the transistor, either NPN or PNP is arranged to operate the transistor at both sides of the I-V characteristics curves shown below. A transistor can be operated in three modes, active region, saturation region, and cut-off region.

When is a transistor used as a switch?

The transistor will operate as an amplifier or other linear circuit if the transistor is biased into the linear region. The transistor can be used as a switch if biased in the saturation and cut-off regions. This allows current to flow (or not) in other parts of a circuit.