TLP291 consists of photo transistor, optically coupled to a gallium arsenide infrared emitting diode。 TLP291 is housed in the SO4 package,very small and thin coupler。Since TLP291 is guaranteed wide operating temperature (Ta=-55 to 110 ˚C) and high isolation voltage (3750Vrms), it’s suitable for high-density surface mounting applications such as small switching power supplies and programmable controllers。