An important parameter for the characterization of an optocoupler is the current transfer ratio or CTR. The CTR is the ratio between the output current of the phototransistor and the input current of the infrared LED multiplied by 100%. The optocouplers are available with different binning groups having minimum and maximum values and the range of a binning is usually in a 2:1 ratio. The binning is estimated with a defined collector-emitter voltage and forward current.