Photocells

Excelitas' photocell Light-Dependent Resistor can provide a very economical and technically superior solution for many applications where the presence or absence of light is sensed (digital operation) or where the intensity of light needs to be measured (analog operation).

Semiconductor light detectors can be divided into two major categories: junction and bulk-effect devices.   The bulk-effect photoconductors have no junction. 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, Excelitas refers to its 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. 

Key Features of our Photocells:

• Lowest-cost visible detector
• Available in low-cost plastic-encapsulated packages as well as hermetic packages (TO-46, TO-5, TO-8)
• Responsive to both very low light levels (moonlight) and to very high light levels (direct sunlight)
• Wide dynamic range: resistance changes of several orders of magnitude between “light” and “no light”
• Low noise distortion
• Maximum operating voltages of 50 to 400 volts are suitable for operation on 120/240 VAC
• Available in center-tap dual-cell configurations as well as specially selected resistance ranges for special applications
• Easy to use in DC or AC circuits
• Usable with almost any visible or near-infrared light source such as LEDs, neon, fluorescent, incandescent bulbs, lasers, flame sources, sunlight, etc.
• Available in a wide range of resistance values