The PS8551AL4 is an optically coupled isolation amplifier that uses an IC with a high-accuracy sigma-delta A/D converter and a GaAIAs light-emitting diode with high-speed response and high luminance efficiency on the input side, and an IC with a high-accuracy D/A converter on the output side. The PS8551AL4 is designed specifically for high common mode transient immunity (CMTI) and high linearity (nonlinearity). The PS8551AL4 is designed for current and voltage sensing.