A photodiode array (PDA) is just many photodiodes stacked together. The individual photodiodes are called pixels or elements. PDAs are particularly useful because they can measure photons in the NIR region, which a CCD cannot. The PDAs used in StellarNet’s NIR spectrometers are made of an InGaAs alloy and come with 512 or 1024 pixels in a linear array. The individual pixels are 25 x 500 µm.
