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Characteristics And Applications of working Principle


Photodiode :

A photodiode is one style of a light-weight detector, wont to convert the sunshine into current or voltage supported the mode of operation of the device. It includes optical filters, intrinsical lenses and additionally surface areas. A junction photodiode is an associate intrinsic device that behaves equally to a standard signal diode, however, it generates a photocurrent once a light-weight is absorbed within the depleted region of the junction semiconductor. A photodiode may be a quick, extremely linear device that exhibits high quantum potency supported the applying and will be employed in a range of various applications.

they’re designed to figure in reverse bias mode, that means the p-side of the diode is connected to the negative terminal of the battery and then-side the positive. It produces photocurrent by generating electron-hole pairs, because of the absorption of sunshine within the intrinsic or depletion region. The photocurrent so generated is proportional to the absorbed candlepower. The electrons and holes could stay free, or alternative electrons could mix with holes to create complete atoms once more within the space lattice. However, it’s doable that the electrons associated holes could stay free and be a force far away from the depletion region by an external field. during this method, the present through the diode can modification and a photocurrent is made.

Working Principle of Photodiode :

Photodiodes square measure alike to regular semiconductor diodes, however that they will be either visible to let lightweight reach the fragile a part of the device. many diodes supposed to be used precisely as a photodiode also will use a Pin junction somewhat than the standard P-N junction. lightweight energy will be thought about in terms of photons or packets of sunshine. once a gauge boson of sufficient energy enters the depletion region of a semiconductor, it should strike Associate in Nursing atom with sufficient energy to unharness the lepton from the atomic structure.

A photodiode could be a p–n junction or Pin structure. once a gauge boson of sufficient energy strikes the diode, it creates Associate in Nursing electron-hole try. This mechanism is additionally called the inner physical phenomenon impact. If the absorption happens within the junction’s depletion region, or one diffusion length aloof from it, these carriers square measure sweptwing from the junction by the inbuilt force field of the depletion region. The add of photocurrents and dark currents, that flow with or while not lightweight, is that the total current passing through the photodiode. The sensitivity of the device will be raised by minimizing the dark current.

Types of Photodiode :

  • P-N Photodiode.
  • Schottky ikon Diode.
  • Pin Photodiode.
  • Avalanche Photodiode.

The totally different sorts of photodiode have slightly different modes of operation, however, all think about the identical bedrock of operation. though there are varied sorts of photodiode accessible within the market and that they all work on identical basic principles, although some are improved by alternative effects. The operating of totally different of various sorts of photodiodes add a rather different method, however, the essential operation of those diodes remains identical.

Modes of Operation :

The operative modes of the photodiode embrace 3 modes,


  • particularly electrical phenomenon mode.
  • electrical conduction mode.
  • avalanche diode mode.

Photoconductive mode The diode employed in this mode is additional usually reverse biased id est the cathode becomes positive with relevance the anode. the applying of reverse voltage will increase the breadth of the depletion layer, that successively reduces the latency and capacitance of the junction. This mode is incredibly quick and exhibits electronic noise. A semiconductor photodiode may be operated in either the electrical phenomenon or electrical conduction mode. within the electrical phenomenon mode, the photodiode is unbiased; whereas for the electrical conduction mode, Associate in Nursing external reverse bias is applied. Mode choice depends upon the speed needs of the applying, and also the quantity of dark current that’s tolerable. within the electrical phenomenon mode.

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