Name: Vacuum Tubes and Semiconductors
Uploaded: 2019-07-19
Duration: 8 min 14 s
Description: Vacuum tubes were the first devices where the electronic discharge was realised. Further work on them gave birth to semiconductor electronics. Let's discuss...

Question

What is a diode valve? Show how a diode valve can be used as a rectifier?

Accepted Answer

A diode valve is a vacuum tube device that contains two electrodes- cathode and anode. Cathode is in the form of nickel cylinder coated with barium and is heated indirectly. This thermal energy gets converted into kinetic energy which results in the emission of electrons from the cathode. This emission of electrons leave a positive charge on the cathode, which is able to attract some electrons back towards it. Electrons having higher energy gets farther away from cathode and reach the anode. In this way, electrons travel from cathode to anode and results in the flow of unidirectional current.

Current in a diode in unidirectional i.e, it can only flow in one direction. Therefore, if an alternating signal is applied to the diode, then it will only conduct half a cycle. Hence, rectifying the signal in the process. Hence, a diode can be used to convert an AC signal into a DC signal and can be used as a rectifier.

Diode can be used as a rectifier in two ways- half-wave rectifier and full-wave rectifier. Half-wave rectifier is the most basic version of diode valve rectifier. It only uses one diode and is not as efficient as full-wave rectifier. A full-wave rectifier, uses two diodes, and is more efficient as it conducts both halves of an alternating waveform cycle.

What is a diode valve? Show how a diode valve can be used as a rectifier?

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