difference between optocoupler and opto isolator

The designer can compensate for aging by doing several things: This had implications for the optocoupler’s long-term stability and operation, especially at high temperature operation. This is largely due to the electrical and thermal stressing of the PN junction. The quantum efficiency of the LED, defined as the total photons per electron of input current, decreases with time at a constant current. Basic operation of opto vs capacitive coupled CMOS isolatorįigure 2 shows examples of X-ray images of an opto-coupler assembly (left) and a digital isolator assembly (right) to help visualize the physical construction of these devices.Ī prominent characteristic of the opto is the aging problem. Optos were basically the only solution available until CMOS-based digital isolators were developed in the late 1990s using inductive (magnetic) or capacitive coupling to transfer the signal.įigure 1 highlights the technology differences between opto-couplers and digital isolators.įigure 1. They were all basically some sort of light-emitting structure (the miniature bulbs were replaced by a semiconductor-based light emitting diode or LED) on the primary side, coupled with various forms of light-sensitive devices such as a photo-resistor, photo-transistor, photo-diode or triac that made the device suitable for a range of dc and ac applications. Later developments introduced more sophisticated opto-coupled devices that made the system designer’s job a little easier. Earliest forms consisted of miniature incandescent light-emitting bulbs on the primary side, a clear (optically transparent) plastic, which acted as the insulation or dielectric layer as well as the optical path, and a photo-resistor on the secondary side, whose resistance was modulated by the amount of light falling on it. The first patents for optos were issued in the 1960s. The earliest isolators were optically-coupled devices, also called opto-isolators or optocouplers, “optos” for short. The insulation barrier also safeguards equipment and human operators from high voltages. Galvanic isolators are devices that couple an electrical data or control signal across an insulation barrier without any flow of current through it, thereby enabling signals to be transferred while blocking noise. These challenges can be solved by introducing galvanic isolators in the circuit design.

Preventing electrical noise from corrupting sensitive signals.Effective communication across sub-systems with relatively high ground potential differences.Providing safety from high voltages – for electronic control equipment as well as human operators.The design of modern electronic systems in applications are as varied as industrial automation, power supplies for telecom base stations, and on-board chargers (OBC) for electric vehicles (EV) and comes with a unique set of challenges:

Difference between optocoupler and opto isolator