Editing Opto-isolator (section)

{{about|the electronic component|the optical component|optical isolator}}
{{short description|Insulates two circuits from one another while allowing signals to pass through in one direction}}
[[File:Optoisolator Pinout.svg|class=skin-invert-image|thumb|right|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<ref group=note>Real-world schematic diagrams omit the barrier symbol, and use a single set of directional arrows.</ref>]]

An '''opto-isolator''' (also called an '''optocoupler''', '''photocoupler''', or '''optical isolator''') is an [[electronic component]] that transfers electrical [[Signal|signals]] between two isolated circuits by using light.<ref>Graf, p. 522.</ref> Opto-isolators prevent [[high voltage]]s from affecting the system receiving the signal.<ref name=L2>Lee et al., p. 2.</ref> Commercially available opto-isolators withstand input-to-output voltages up to 10&nbsp;[[Volt|kV]]<ref name=H145>Hasse, p. 145.</ref> and voltage transients with speeds up to 25&nbsp;kV/[[microsecond|μs]].<ref name=J279>Joffe and Kai-Sang Lock, p. 279.</ref>

A common type of opto-isolator consists of an [[Light emitting diode|LED]] and a [[phototransistor]] in the same opaque package. Other types of source-sensor combinations include LED-[[photodiode]], LED-[[thyristor#Photothyristors|LASCR]], and [[lamp (electrical component)|lamp]]-[[photoresistor]] pairs. 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.