Amplifier Noise
Input-referred noise sets the detection floor. σ_amp = e_n.
Read floor (DN)
2.52
Quantisation g/√12 = 0.58 e⁻
Shot noise (e⁻)
31.6
Total noise (e⁻)
32.0
Total SNR
31.2
Min Detectable (3σ)
20.26 e⁻
σ_total = √(S + eₙ² + g²/12) — quadrature sum of shot noise, amplifier noise and ADC quantisation (g in e⁻/DN)
SNR = S / σ_total — at high signal, shot noise (√S) dominates; at low signal, amplifier noise (eₙ) dominates
S_min = (9 + √(81 + 36·σ_r²)) / 2 with σ_r² = eₙ² + g²/12 — signal at which total SNR = 3
Model and references
Textbook approximation. A standard approximation from the literature (for example paraxial, plane-wave or Gaussian-beam), valid within the range the page states. About the tiers
Poisson shot noise √S added in quadrature to a signal-independent input noise; ADC quantisation g/√12 adds to the read floor; minimum detectable signal at SNR = 3. Dark charge, fixed-pattern noise and excess noise are left out.
- Janesick J. R. (2007). Photon Transfer. SPIE Press. Read-noise, shot-noise and dark-noise regimes; total noise as the quadrature sum. doi:10.1117/3.725073