Photocoupler. Solid State Relay, OCMOS FET. The PS7804-1A is a low output capacitance solid state relay containing a GaAs LED on the light emitting side (input side) and MOS FETs on the output side. An ultra small flat-lead package has been provided which realizes a reduction in mounting area of about 50% compared with the PS72xx series. It is suitable for high-frequency signal control, due to its low C x R, low output capacitance, and low off-state leakage current.