A 250 V depletion-mode switch in a SOT-23
The Infineon BSS139H6327XTSA1 is an N-channel depletion-mode MOSFET from the SIPMOS® series, rated for a drain-to-source voltage of 250 V and a continuous drain current of 100 mA at 25°C. The depletion-mode (normally-on) characteristic means the channel conducts at zero gate-source voltage, requiring a negative Vgs to turn it off — a feature that suits current-source, cascode, and normally-on start-up circuits where an enhancement-mode part would not work.
Parametric profile for a signal-level high-voltage FET
Gate charge is 3.5 nC at 5 V, and input capacitance is 76 pF at 25 V drain bias — these low values keep switching losses minimal in low-frequency or soft-switching applications. Maximum power dissipation is 360 mW at ambient temperature — the SOT-23 package limits heat sinking, so the 100 mA current rating assumes adequate PCB copper area for thermal relief.
