What is Photodiode? | Explained its Working and Application
A photodiode is a PN junction light-sensitive semiconductor device that when exposed to radiation, produces an electrical current. It means a photodiode receives light as input and generates current as output.
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Video Summary:
Photodiode vs LED:
- The function of a photodiode is the opposite of an LED. An LED is also a diode but makes light out of electricity.
Photodiode Terminals:
- There are two terminals that protrude from the end of a photodiode. The cathode terminal is the diode's shorter end, whereas the anode terminal is the diode's longer end.
Photodiode Symbol:
- The photodiode symbol is nearly similar to the symbol of the PN junction diode, except that it includes two inward arrows representing light shining on a photodiode. The symbol also indicates the two terminals of a photodiode: cathode and anode.
Photodiode Construction:
- If you are familiar with diodes, you know that in a PN junction, the P region majority carriers are holes, and the N region majority carriers are electrons. Also, there is a space in between, called the depletion region, which has no electrons or holes but only includes positive (or donor) ions, and negative (or acceptor) ions.
Photodiode Dark Current:
- When the photodiode is under the reverse bias condition and in the absence of the incident light, only a minority reverse saturation current in the microampere goes through the photodiode, called the dark current.
Photodiode Working Principle:
- It’s time to shine light over the depletion region of the photodiode to see what happens. If incident photons have enough energy, they can release electrons from the valence band and occupy them in the higher energy band called the conduction band.
- Therefore, we can see a free electron and a free hole have been generated within the depletion region. Because of the movement of these charge carriers, which is the result of throwing light, the electric current, known as photocurrent, is generated in the photodiode.
Photodiode Advantages and Disadvantages:
- The main advantages of using a photodiode are low noise, reasonable price, lightweight, small and compact, long lifespan, no need for high voltage, fastest photodetector, mechanical stress-tolerant, and the output current has linearity as a function of incident light.
- The main disadvantages of using a photodiode are the need for external biasing, with a rise in temperature, the dark current increases, the active area is small, and the amplification is needed since the output is low.
Photodiode Application Example:
- Finally, let us explore an application where the photodiode is used in an alarm system. Here we have a welding robot, and we do not want anyone to be present when the welding operation is going on since it may cause injury to the personnel.
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⏰ TABLE OF CONTENTS ⏰
00:00 Photodiode Definition
00:41 Photodiode Symbol
01:04 Photodiode Diagram
02:54 Photodiode Dark Current
03:34 Photodiode Working Principle
05:22 Photodiode Pros and Cons
05:59 Photodiode Application
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