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VT400 参数 Datasheet PDF下载

VT400图片预览
型号: VT400
PDF下载: 下载PDF文件 查看货源
内容描述: 感光细胞和模拟光隔离器( Vactrols ) [Photoconductive Cells and Analog Optoisolators (Vactrols)]
分类和应用:
文件页数/大小: 76 页 / 1202 K
品牌: PERKINELMER [ PERKINELMER OPTOELECTRONICS ]
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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.  
Figure 2  
Bulk Effect Photoconductor (Photocell)  
In contrast, bulk effect photoconductors have no junction. As shown in  
Figure 2, the bulk resistivity decreases with increasing illumination,  
allowing more photocurrent to flow. This resistive characteristic gives  
bulk effect photoconductors a unique quality: signal current from the  
detector can be varied over a wide range by adjusting the applied  
voltage. To clearly make this distinction, PerkinElmer Optoelectronics  
refers to its bulk effect photoconductors as photoconductive cells or  
simply photocells.  
Photocells are thin film devices made by depositing a layer of a  
photoconductive material on a ceramic substrate. Metal contacts are  
evaporated over the surface of the photoconductor and external  
electrical connection is made to these contacts. These thin films of  
photoconductive material have a high sheet resistance. Therefore, the  
space between the two contacts is made narrow and interdigitated for  
low cell resistance at moderate light levels. This construction is shown  
in Figure 3.  
Figure 1  
Junction Photoconductor (Photodiode)  
Figure 3  
Typical Construction of a Plastic Coated Photocell  
2