Support on principles for the use of phototransistor optocouplers

Würth Elektronik has extended its collection of practical information to support electronics developers with the new AppNote ANO007 'Understanding Phototransistor Optocouplers'. Optocouplers, also known as photocouplers or optoisolators, are components that send an electrical signal using an optical coupling between two galvanically separated circuits. An important aspect of the development of robust applications involving optocouplers is not only to understand and integrate their main parameters but also to take the possible effects of their parasitic elements into consideration. A profound understanding of these aspects and the precise consideration of tolerances, deviations, and interdependences are indispensable. The new application note starts by explaining the principles and presents comprehensive experimental results gained with the company's WL-OCPT optocouplers.

Optocouplers provide high isolation voltage (5kV) in connection with a very compact form factor. In contrast to transformers and capacitors, which can only transmit AC signals, the optocouplers send AC and DC signals. This makes them especially appealing for applications such as isolated communication interfaces, high-voltage motor drives, AC grid monitoring, control circuits for power-supply stations, industrial I/O modules, or sensor systems. The AppNote provides instructions on the characterisation of parameters and on important aspects that must be considered from the design aspect.