Current transfer ratio (CTR) is a parameter of photocouplers, which is expressed as a percentage indicating the ratio of the output current (Ic) to the input current (If). Ensuring your circuit has sufficient CTR needs to be considered when designing, otherwise the photocoupler’s output may be too small and cause malfunctions.
Different ranks of CTR:
The breakdown of part number:
The default CTR RANK option code is none if no request for a specific CTR rank is made. Then you will receive either one of CTR. If you need a specific CTR rank, you should include that request in the “Order Notes” section of your Digi-Key order, or inform your Customer Support representative of this requirement when placing an order.
You can look at the rank code on the top marking to confirm CTR of physical parts.
Current Transfer Ratio - CTR