Why should a Würth Elektronik optocoupler be chosen? Würth Elektronik optocouplers use the coplanar structure which ensures the fixed isolation gap for high product stability. Due to the coplanar structure the CTR is also stable over the whole temperature range. Furthermore, the optocoupler is made with a copper leadframe for high reliability and solderability, as well as thermal and electrical conductivity. The structure is made for high CTR in low current operation.