60 V, 20 A rectifier — FERD structure, not Schottky
The STMicroelectronics FERD20M60ST is a 60 V, 20 A Field Effect Rectifier Diode (FERD) in a TO-220 through-hole package. It is not a Schottky barrier diode — the FERD structure delivers a forward voltage of 560 mV at the full 20 A rated current, which is competitive with Schottky devices at this voltage class, but with a different reverse leakage profile. The fast-recovery characteristic (≤ 500 ns at > 200 mA) suits it for line-frequency rectification and low-speed switching applications where recovery losses matter less than conduction loss.
Forward voltage and thermal budget
At 20 A forward current the maximum Vf is 560 mV — this sets the conduction loss floor at roughly 11.2 W at full load. The junction is rated to 175 °C maximum, so the TO-220 package must be mounted on an adequate heatsink to keep Tj within limits; the copper tab area and airflow determine the real thermal resistance. Reverse leakage is 230 µA at the 60 V rated reverse voltage — higher than a typical ultrafast diode at this voltage, but the trade-off is the lower forward drop. In a 20 A output rectifier the leakage contribution to total loss is negligible at room temperature but rises with junction temperature.