Choosing the right APD (Avalanche Photodiode)


Avalanche Photodiodes (APD) are generally recommeneded for use in high bandwidth applications or where internal gain is required to overcome high preamplifier noise.
The guidelines laid out below may help to decide whether an APD is the most appropriate device for your light detection application.

  1. Determine the wavelength range to be covered.
    Most APDs fall within the wavelength range from 300nm to 1700nm. Each types of APD can cover different ranges of wavelength and has different characteristics.
Type of APDs Silicon Germanium InGaAs
Wavelength 300nm to 1100nm 800nm to 1600nm 900nm to 1700nm
Characteristics Extensive APD product range Cost-sensitive applications, suitable to work in high EMI environment Lower noiser, higher bandwidth relative to active area
  1. Determine the minimum size of the detector that can be used in the optical system.
    Effective optics can often be more cost-effective than the use of larger APDs.

  2. Determine the required frequency bandwidth of the system.
    Most importantly, over-specifying bandwidth will degrade the SNR of the system.