Photodiode Cutoff Wavelength Formula and Calculator

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cutoff wavelength
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The cutoff wavelength is a key parameter that defines the spectral response limit of a photodiode. This guide explains the formula for calculating cutoff wavelength and provides a convenient calculator for accurate results.

Definition

To build up leakage current in the photodiode, the energy of the photon must be greater than or equal to the energy band gap between the valance and conduction band, called the band gap (Eg).

  • h*v >= Eg

h*c/λ >= Eg

or

λ <= h*c/Eg

So, the threshold for conduction or detection is commonly called the long wavelength cutoff point (λc).

λc = h*c/Eg

Photodiode Responsivity Calculator and Example

Inputs

Outputs

Here’s an example using the photodiode responsivity calculator:

INPUTS:

  • Eg = 1.42 eV

OUTPUTS:

  • λ = 873.23 nm

Photodiode Cutoff Wavelength Formula

The following formula is used in this photodiode cutoff wavelength calculator:

Photodiode Cutoff Wavelength Equation

Image Alt: Photodiode Cutoff Wavelength Equation, formula

Conclusion

Understanding the cutoff wavelength is vital for selecting and designing photodiodes for specific applications. Use the formula and calculator provided to ensure precise spectral response analysis.

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