35 ns trr — the switching loss number that matters
The VS-MURB820-M3 is a Vishay FRED Pt® ultrafast plastic rectifier rated for 200 V reverse and 8 A average forward current. Its 35 ns reverse recovery time (trr) is the spec that determines switching losses in a 100 kHz PFC boost stage or a flyback snubber — every nanosecond of stored charge that has to be swept out adds to the junction temperature rise.
Forward drop and thermal budget
At the rated 8 A forward current the maximum forward voltage is 975 mV. That 7.8 W conduction loss at full load has to be sunk through the TO-263AB (D²PAK) package's exposed pad — the board copper area under the tab sets the junction-to-ambient thermal resistance.
Surface-mount in a TO-263-3 (D²PAK) case — two leads plus the tab. The footprint is shared with the standard D²PAK outline; the tab is the cathode. Reverse leakage is 5 µA at the 200 V rated blocking voltage, which is low enough that it does not shift the bias point in a voltage-multiplier string.
The FRED Pt® series is Vishay's established ultrafast family; the -M3 suffix indicates the ROHS3-compliant version.