The Infineon BSS169H6327XTSA1 is an N-channel depletion-mode MOSFET from the SIPMOS® family, packaged in a standard SOT-23-3. Unlike enhancement-mode FETs that are normally off, this device conducts at zero gate-source voltage and requires a negative Vgs to turn off — a characteristic that makes it the natural choice for current-source biasing, start-up circuits in switched-mode power supplies, and cascode stages where a normally-on pass element is needed. Rated for 100 V drain-source and 170 mA continuous drain current. The 6 Ohm on-resistance at 10 V drive is typical for a depletion-mode device at this current level.
Drive voltage and gate characteristics
The drive voltage range spans 0 V to 10 V, with the maximum Rds(on) specified at 10 V. Gate threshold is 1.8 V maximum at 50 µA drain current. Maximum gate-source voltage is ±20 V. Gate charge is 2.8 nC at 7 V, and input capacitance is 68 pF at 25 V drain-source — both low enough for switching frequencies into the hundreds of kilohertz without excessive drive losses. The small gate charge also means a simple RC drive circuit is often sufficient.
Power handling and thermal considerations
Maximum power dissipation is 360 mW at 25°C ambient. The 170 mA continuous current rating is tied to the same thermal limit.