What is the conversion efficiency?
The figure below shows a general circuit using a transistor coupler. If the LED current IF is run to the input side, the collector current IC will run to the output side. This current transfer ratio is called the conversion efficiency (CTR: Current Transfer Ratio) and expressed by (IC/IF) × 100 (%). As with hFE for the transistors, the conversion efficiency is an important parameter for the transistor couplers.
