Unlike photocouplers, MOSFET relays can switch either DC or AC loads and the output switching current is not affected by input current. So MOSFET relays can be operated by very small currents. The MOSFET relays have much smaller leakage current (a mere 1 nA) when in off-state compared to photocouplers and phototriacs. Also, the small heat generated does not require a heat sink.