●What is a Photoconductive Cell?
●Semiconductor light detectors can be divided into two major categories: junction and bulk effect devices. Junction devices, when operated in the photoconductive mode, utilize the reverse characteristic of a PN junction. Under reverse bias, the PN junction acts as a light controlled current source. Output is proportional to incident illumination and is relatively independent of implied voltage as shown in Figure 1. Silicon photodiodes are examples of this type detector.
●Applications
●Photoconductive cells are used in many different types of circuits and applications.
●Analog Applications
●• Camera Exposure Control
●• Auto Slide Focus - dual cell
●• Photocopy Machines - density of toner
●• Colorimetric Test Equipment
●• Densitometer
●• Electronic Scales - dual cell
●• Automatic Gain Control - modulated light source
●• Automated Rear View Mirror
●Digital Applications
●• Automatic Headlight Dimmer
●• Night Light Control
●• Oil Burner Flame Out
●• Street Light Control
●• Absence / Presence (beam breaker)
●• Position Sensor
