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#OPTICAL ISOLATOR CIRCUIT SERIES#

The symbol shows the LED, which is normally used as the light emitter. The opto-coupler symbol used in circuit diagrams indicates the function and internal elements within the overall component. However the terms are still widely used interchangeably. This is a rough guide to the differences between optocouplers and optoisolators. Opto-isolator: The opto-isolator is generally used in power systems and used to transmit analogue or digital information between circuits where the potential difference is above 5 000 volts.

Opto-coupler: The opto-coupler is generally thought of as being used to transmit analogue of digital information between circuits while maintaining electrical isolation at potentials up to 5 000 volts.The distinguishing factor between the opto-coupler and opto-isolator is in the voltage difference expected between the input and output: Strictly, there are differences between the terms optoisolator and optocoupler. The terms photocoupler, optocoupler and opto-isolator are often used interchangeably within electronics and technical literature when referring to components that undertake the same function. However the mechanical arrangements need to be considered and this often makes an opto-coupler made from separate devices less convenient, although for opto-isolators there may be the need to utilise separate components for some applications. The opto-coupler may also include an output amplifier.Īlthough an opto-coupler or opto-isolatoris usually thought of as a single integrated package, it is possible to achieve the same result using separate devices.

#OPTICAL ISOLATOR CIRCUIT SERIES#

The opto-coupler may also contain other circuitry as well, For example it may include the series resistor for the LED or even the drive capability for the diode. The light emitter and detector are tailored to match one another, having matching wavelengths so that the maximum coupling is achieved. The light detector can be any one of a number of different types of device from a photodiode to a phototransistor, photodarlington, etc.

Light detector: The light detector within the opto-coupler or opto-isolator detects the light from the emitter and converts it back into an electrical signal.

Typically the light emitter is a light emitting diode.

Light emitter: The light emitter is on the input side and takes the incoming signal and converts it into a light signal.

The opto-coupler is a component that contains the two elements required for an opto-isolator: Optocoupler Photocoupler / Opto-coupler basics As a result, optical couplers or photocouplers are found in a surprisingly high number of circuits. They even form the essential element in solid state relays where an optical coupling is used to isolate the input and output electrically, whilst enabling the output to be switched according to the input state. Photocouplers or optocouplers are used to provide many functions: they can be used to link data across two circuits, they can be used within optical encoders, where the optocoupler provides a means of detecting visible edge transitions on an encoder wheel to detect position, etc., and they can be used in many other circuits where optical links and transitions are needed. The photocouplers or optocouplers are typically contained in a single package, often about the size of an integrated circuit, although there is a large degree of variation according to the intended application. Optocouplers can be described by a variety of different names including optoisolator, and photocoupler.Įssentially an optocoupler or photocoupler is a semiconductor device that uses a short optical path or link to couple a signal from one electrical circuit to another whilst providing electrical isolation. Phototransistor basics Applications & circuits Photodarlington Optocoupler / optoisolator Photocouplers, Opto-couplers & Opto-isolators Optocouplers & optoisolators use LEDs, photodiodes & phototransistors & are used to link circuits together, but isolating them electrically.