Photodiode responsivity calculator
At 850 nm and 80% external quantum efficiency, responsivity is 0.5485 A/W: 1 microwatt produces 0.5485 microampere. Calculate quantum efficiency, current, shot noise, NEP, bandgap cutoff and LED photon energy.
| Ideal responsivity (QE = 1) | 0.6856 A/W |
|---|---|
| Responsivity | 0.5485 A/W |
| External quantum efficiency | 0.8 |
| Photocurrent | 5.485e-7 A |
| Signal shot noise (RMS) | 1.326e-11 A |
| Dark shot noise (RMS) | 5.661e-13 A |
| Total shot noise (RMS) | 1.327e-11 A |
| Dark shot-noise NEP | 3.264e-14 W/sqrt(Hz) |
| Illuminated shot-noise NEP | 7.651e-13 W/sqrt(Hz) |
| Bandgap cutoff estimate | 1107 nm |
| LED photon energy | 1.459 eV |
| LED photon energy | 2.337e-19 J |
R = eta e lambda/(hc) = eta lambda[um]/1.23984 A/W (rounded denominator); eta = R hc/(e lambda), Iph = R P. Noise RMS = sqrt(2 e I B); independent signal and dark variances add. Dark NEP = sqrt(2 e Id)/R in W/sqrt(Hz); illuminated NEP uses Iph + Id. Unity gain only; excludes Johnson, amplifier, 1/f and avalanche noise. R = 0 gives no NEP. Cutoff = hc/(e Eg) is an energy threshold, not a measured response curve; material choice only changes the cutoff, not the entered QE. E_LED = hc/lambda, not forward voltage or electrical efficiency.
Hamamatsu, Si photodiodes technical note; CODATA 2018; Hamamatsu (Si 1.12 eV); Ioffe NSM (Ge 0.661 eV); Liu et al. (2024), In0.53Ga0.47As 0.74 eV; room temperature.
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Example: What photocurrent does 1 microwatt at 850 nm and 80% QE produce?
Reference cases
| Wavelength (nm) | Ideal responsivity (QE = 1) (A/W) | LED photon energy (eV) |
|---|---|---|
| 405 | 0.32665 | 3.0613 |
| 650 | 0.52426 | 1.9074 |
| 850 | 0.68557 | 1.4586 |
| 1310 | 1.0566 | 0.94644 |
| 1550 | 1.2502 | 0.7999 |
Cite this
ScienceShot. Photodiode responsivity calculator. https://scienceshot.com/photodiode-responsivity-calculator.
Sources: Hamamatsu, Si photodiodes technical note: responsivity, quantum efficiency, shot noise and NEP; CODATA 2018 (Tiesinga et al., 2021), exact h, c and e; Si 1.12 eV (300 K): Hamamatsu, Silicon photomultipliers: The ultimate photosensor? (2017), silicon bandgap; Ge 0.661 eV (300 K): Ioffe Institute NSM Archive, Germanium: band structure, basic parameters at 300 K; In0.53Ga0.47As 0.74 eV (300 K): Liu et al., Low-Temperature Growth of InGaAs Quantum Wells Using Migration-Enhanced Epitaxy (2024), lattice-matched In0.53Ga0.47As.
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Cite this page
ScienceShot. (2026). Photodiode responsivity calculator [Online calculator]. https://scienceshot.com/photodiode-responsivity-calculator
@misc{scienceshot-photodiode-responsivity-calculator-2026,
author = {{ScienceShot}},
title = {{Photodiode responsivity calculator}},
year = {2026},
note = {Online calculator},
url = {https://scienceshot.com/photodiode-responsivity-calculator}
}