The Infineon BSS138N E6433 is a small-signal N-channel MOSFET from the SIPMOS® family, housed in a SOT-23-3 package. The maximum on-resistance is 3.5 Ohm at a gate drive of 10 V and 230 mA drain current. These ratings place it in the class of logic-level-compatible switching transistors used for low-current loads, level shifting, and signal switching in mixed-voltage designs. The gate threshold voltage maximum is 1.4 V at 250 µA drain current, and the recommended drive voltage range for achieving rated Rds(on) is 4.5 V to 10 V. Gate charge is a low 1.4 nC at 10 V, keeping switching losses minimal in high-frequency applications.
The wide temperature grade also suits avionics and downhole applications where ambient extremes are common. Maximum power dissipation is 360 mW at 25°C ambient, so thermal management in a SOT-23 package is limited — keep the duty cycle low or add a heatsink pad for continuous operation near the current limit.
Lifecycle status — obsolete, sourced to order
This means Infineon no longer produces it, and the primary supply channel is the independent distribution market.
The small footprint is useful for dense boards, but the 360 mW power limit means the package cannot dissipate much heat — derate the current if the ambient temperature exceeds 25°C.