A synchronous or active rectifier is a circuit that uses a MOSFET for rectification instead of a diode. The advantage of using a MOSFET is that the power lost in high current rectification is lower than with a diode. The other advantage is that the circuit using it need not be in continuous conduction mode.
Reverse Leakage current characteristics:
http://everycircuit.com/circuit/6468904220884992
It's forward quiescent current characteristics is identical.
The zener diode in the circuit prevents the driver's output voltage from swinging beyond 15V from the source of the MOSFET.
This circuit is based on @walkemm's ideal diode circuit:
http://everycircuit.com/circuit/6669969281777664
