ABSTRACT
The P-N or PIN photodiode is usually utilized in applications where speed–response or linearity is required. The photodiode can switch in a few nanoseconds and respond linearly to input levels over nine orders of magnitude. The photodiode output is proportional to the level of illumination and is normally amplified. The voltage output increases as more light energy impinges on the photodiode. The photons impinging on the photodiode generate a voltage potential. The photointegrated circuit is the easiest unit to interface to because it is normally specified to be compatible with logic circuitry and is usually guaranteed to operate under specified conditions over a broad temperature range. The common-emitter circuit will generate an output signal that transitions from high to low when the phototransistor detects light or infrared radiation. The future trend will be toward availability of more special function options, decreasing price, and erosion of discrete photosensor applications as these units become more widely used.
