Why SCRs, Diodes, Transistors are called Active Device?

Hey, today we are going to know why SCRs, Diodes, and Transistors are called Active Devices. According to the energy required for operation, there are two types of electronic components or devices one is an active device and another is a passive device. First of all, let's know what is the active device and passive device.

Active Device: Active devices are those semiconductor devices that need some voltage to start their operation. For example, diode transistors

Passive Device: Passive devices are those semiconductor devices which does not need any voltage to start their operation. For example, resistor, inductor, and capacitor

Why Diode is called an Active Device?

The diode is an active device because to start its operation we need to give some voltage across it. The small voltage to start the operation of the diode is called the Threshold Voltage.

We know that the threshold voltage of a silicon diode is 0.7V which implies that the diode will start its operation after giving 0.7V across it. Until the voltage across the diode reaches or crosses the threshold voltage it doesn't conduct current through it so a minimum voltage must be required to start its operation. 

The threshold voltage of a germanium diode is 0.3V

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Why Transistor is called Active Device?

Transistor also needs some voltage to start its operation that's why it is called Active Device. To properly operate a transistor we need to give proper biasing. A transistor is nothing but a connection of two PN Junction Diodes. In fact, in a Transistor, we need to give two voltages. For example, in a BJT we need to give voltage across Collector to the Base and Emitter to the Base. As it is a combination of two diodes, it also needs some threshold voltage to start its operation. In short, the transistor also needs some power supply for its operation.

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Why SCR is Called Active Device?

SCR means Silicon Controlled Rectifier. SCR is a semiconductor device that needs some voltage across it to start its operation that's why it is called Active Device. SCR also has PN junctions. It has four layers and three junctions. We need to give sufficient voltage across its junctions to start the current conduction through it.

Read Also:

• Why NPN Transistors are mostly used than PNP Transistors?
• SCR Triggering / SCR Turn On Methods Full explanation.

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