Fast recovery diode for MIL-grade signal and bias supplies
The 1N6638US is a standard fast recovery diode from Microchip Technology, qualified to MIL-PRF-19500/578. With a 4.5 ns reverse recovery time, it handles high-speed switching in rectifier and freewheeling applications without the stored-charge penalty of a general-purpose 1N400x-class part. Rated for 125 V DC reverse voltage and 300 mA average forward current, it fits signal-level power rails, bootstrap supplies for gate drivers, and snubber networks where the peak repetitive current stays within the 300 mA average ceiling.
Parametric fit: speed, capacitance, and thermal envelope
The 4.5 ns trr places it in the ultrafast recovery class — the stored charge clears before the next switching edge at frequencies above 100 kHz, so the diode does not conduct through the reverse recovery interval and overheat the junction. This matters for a 300 mA boost converter running at 500 kHz where a slower diode would double the switching loss. Junction capacitance is 2.5 pF at 0 V bias, 1 MHz — low enough that the diode does not load the switching node in a 10 MHz resonant tank or add significant charge injection in a sample-and-hold front end. Forward voltage is 1.1 V maximum at 200 mA, giving a conduction loss of roughly 220 mW at full rated current, well within the D-5D package's thermal budget. The -65°C to 175°C junction temperature range covers the full military temperature grade. At 125°C ambient the forward voltage drops by roughly 10%, reducing conduction loss, but the reverse leakage at 125 V rises from the 0.5 µA room-temperature spec — budget the leakage into the bias supply's quiescent current allowance.
MIL-PRF-19500/578 qualification and package
Screened to MIL-PRF-19500/578, the 1N6638US carries the full JANTX/JANTXV-level process flow — Group A electrical tests, Group B mechanical and thermal shock, Group C life test, and Group D package integrity. The SQ-MELF D-5D package is a hermetic ceramic surface-mount body with metallized end caps, rated for the full -65°C to 175°C range without moisture sensitivity. No MSL floor life limitation — it can be stored indefinitely in a dry cabinet and reflowed without bake-out.