The STPS340S is a 40 V, 3 A Schottky rectifier in an SMC (DO-214AB) surface-mount package. It is specified for fast recovery — ≤500 ns at >200 mA — which suits it for low-voltage power rectification, freewheeling diodes in DC-DC converters, and reverse-polarity protection where the forward voltage drop directly affects efficiency.
Forward voltage and leakage — the efficiency trade-off
At 3 A forward current the maximum forward voltage is 630 mV — a relatively low drop for a 3 A Schottky, which keeps conduction losses manageable in a 5 V or 3.3 V rail.
The base product number is STPS340; the 'S' suffix indicates the SMC package variant.