The Infineon BC817K40WH6327XTSA1 is a general-purpose NPN transistor in a SOT-323 (SC-70) surface-mount package. It is designed for medium-current switching and amplification in circuits up to 45 V collector-emitter and 500 mA continuous collector current. The 170 MHz transition frequency makes it suitable for low-frequency switching up to a few megahertz and linear amplification in audio and signal-conditioning stages. The DC current gain (hFE) is specified at a minimum of 100 at 100 mA collector current and 1 V Vce, which gives predictable saturation behaviour when driving relays, small solenoids, or LED strings from a microcontroller GPIO through a base resistor.
This means Infineon has announced a final production run, after which the part will no longer be manufactured. For a BOM line using this transistor, the immediate action is to secure inventory through the remaining distribution channel before the last-time-buy window closes. No official successor part number has been published for this specific gain-group and package variant; buyers planning long production runs should evaluate a pin-compatible alternative from the BC817 family (same SOT-323 footprint) with an active lifecycle status.
SOT-323 footprint and thermal handling
The SOT-323 (SC-70) package occupies about 2.0 mm × 2.1 mm of board area, fitting dense layouts. Maximum power dissipation is 250 mW — derate this for ambient temperatures above 25 °C. The junction temperature rating of 150 °C (TJ) sets the upper thermal limit; for continuous operation at 500 mA collector current, ensure the board copper and air flow keep the junction below this ceiling. The 100 nA maximum collector cutoff current (ICBO) is low enough for battery-powered circuits where leakage matters.