Is reverse biasing a photodiode essential?

[abinayabaskaran]

         Although I the basic operations of photodiode while reverse biasing.When practically reverse biasing a diode we ought to give supply to terminals.when we want to measure output in voltage,how can i connect it to same terminal?then then same voltage will be the output rite?

[AJISH ALFRED]

Hi,

Normally its done using a seires resistor connected with the photodiode and the voltage is measured across it.

[abinayabaskaran]

 Yes.But what if photodiode can act only in photovoltaic mode?

[Ganesh Selvaraj]

Your question is not clear. But here is the information I got from another web page:

 

A photodiode can be operated in one of two modes: photoconductive (reverse bias) or photovoltaic (zero-bias). Mode selection depends upon the application’s speed requirements and the amount of tolerable dark current (leakage current).

Photoconductive
In photoconductive mode, an external reverse bias is applied, which is the basis for our DET series detectors. The current measured through the circuit indicates illumination of the device; the measured output current is linearly proportional to the input optical power. Applying a reverse bias increases the width of the depletion junction producing an increased responsivity with a decrease in junction capacitance and produces a very linear response. Operating under these conditions does tend to produce a larger dark current, but this can be limited based upon the photodiode material. (Note: Our DET detectors are reverse biased and cannot be operated under a forward bias.)

Photovoltaic
In photovoltaic mode the photodiode is zero biased. The flow of current out of the device is restricted and a voltage builds up. This mode of operation exploits the photovoltaic effect, which is the basis for solar cells. The amount of dark current is kept at a minimum when operating in photovoltaic mode.

[abinayabaskaran]

yes.that what i mean for many applications photodiode can be used with out biasing.So how can we say it essential to reverse bias a photodiode?some diode are designed only to operate in photovoltaic mode so how can we bias it?

[Ganesh Selvaraj]

No one said its always essential to bias the photodiode. we bias it only when we need to “read” something from it.

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