The majority of opto-isolators on the market use bipolar silicon phototransistor sensors. Commercialization of LED technology in 1968–1970 caused a boom in optoelectronics, and by the end of the 1970s the industry developed all principal types of opto-isolators. They are the slowest, but also the most linear isolators and still retain a niche market in the audio and music industries. Photoresistor-based opto-isolators were introduced in 1968. The value of optically coupling a solid state light emitter to a semiconductor detector for the purpose of electrical isolation was recognized in 1963 by Akmenkalns, et al. Usually opto-isolators transfer digital (on-off) signals and can act as an electronic switch, but some techniques allow them to be used with analog signals. Other types of source-sensor combinations include LED- photodiode, LED- LASCR, and lamp- photoresistor pairs. Ī common type of opto-isolator consists of an LED and a phototransistor in the same opaque package. Commercially available opto-isolators withstand input-to-output voltages up to 10 kV and voltage transients with speeds up to 25 kV/ μs. Opto-isolators prevent high voltages from affecting the system receiving the signal. Īn opto-isolator (also called an optocoupler, photocoupler, or optical isolator) is an electronic component that transfers electrical signals between two isolated circuits by using light. Schematic diagram of an opto-isolator showing source of light (LED) on the left, dielectric barrier in the center, and sensor (phototransistor) on the right.

Opto isolator current transfer ratio