Question

Which material is used for photoconductive cells?

(a) Germanium

(b) Cadmium sulphide

(c) Lithium

(d) Phosphorous

This question was addressed to me during an interview for a job.

My doubt is from Instrumentation Amplifier in division Operational Amplifier Applications of Linear Integrated Circuits

Answer 1

The correct answer is:

(b) Cadmium sulphide

Explanation:

Cadmium sulphide (CdS) is the most commonly used material for photoconductive cells (also known as LDRs - Light Dependent Resistors). It has the property of changing its resistance when exposed to light. In darkness, the resistance of a CdS photoconductive cell is very high, while in the presence of light, its resistance decreases significantly, making it useful for light sensing applications.

• Germanium is used in semiconductors and detectors but is not typically used for photoconductive cells.
• Lithium and Phosphorous are not commonly used materials for photoconductive cells.