Difference between Photovoltaic and Photoconductive mode photodiode

This page compares Photovoltaic mode vs Photoconductive mode and mentions difference between Photovoltaic mode and Photoconductive mode used in photodiode. It mentions links to basics,types,advantages and disadvantages of photodiode.

Photodiode Photovoltaic mode

In photovoltaic mode, When light falls on semiconductor material of photodiode, it can excite electrons to higher energy state. Due to this, electrons become mobile and leave behind holes. The electrons move toward the cathode terminal of the photodiode and holes move toward the anode terminal. This creates voltage between the two terminals. This happens even in the absence of the visible light. The tiny amount of current produced without visible light is known as dark current. It is also called zero-bias mode.

Photodiode Photovoltaic mode vs Photoconductive mode

Photodiode Photoconductive mode

In photoconductive mode, when light falls on photodiode, it creates pairs of electrons and holes in semiconductor material. These move toward opposive directions due to applied bias voltage. As a result small current flows through the photodiode. Photoconductive mode delivers fast response compare to photovoltaic mode. This is due to wider depletion layer and reduction of capacitance which is result of applied reverse bias voltage. It is also called reverse bias mode.

Following table mentions difference between photovoltaic and photoconductive modes of the photodiode.

Photovoltaic mode Photoconductive mode
Zero bias Reverse bias
No "dark" current Has "dark" current
Linear Nonlinear
Low noise (i.e. Johnson) Higher noise (i.e. Johnson, Shot)
Used in precision applications Used in high speed applications

Also refer Photodiode basics and types >> and advantages and disadvantages of Photodiode >> for more information.

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