This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.

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A photodiode array (PDA) is a linear array of discrete photodiodes, based on photovoltaic principle, on an integrated circuit (IC) chip. Light exposure of each photodiode generates a current. The light creates electron-hole pairs and the electrons migrate to the nearest PIN or PN junction as shown in Figure 4910. After a fixed integration time the charge at each element is sequentially read with solid-state circuitry to generate the detector response as a function of linear distance along the array. Modern PDAs are available with 512, 1024, or 2048 elements, e.g. with typical dimensions of ~ 25 µm wide and 1-2 mm high.

One advantage of PDAs is that, with numerous photoreceptors, it is placed at the image plane of a EELS and EDS spectrometer to allow a range of wavelengths to be detected simultaneously, instead of stepping through all the wavelengths mechanically with a monochromator.

Figure 4910. Schematic of a photodiode array (PDA)