Infineon has marked the BCR166E6433HTMA1 as obsolete.
What this pre-biased PNP transistor does
The BCR166E6433HTMA1 is a PNP pre-biased transistor — a single switching transistor with two integrated bias resistors (R1 = 4.7 kOhms, R2 = 47 kOhms) built into the same SOT-23 package. That saves a couple of external resistors and shrinks the board footprint for simple low-current switching, level shifting, or driver stages. The 50 V collector-emitter breakdown and 100 mA collector current rating cover typical 5 V or 12 V logic-level loads, and the 160 MHz transition frequency is fast enough for basic PWM or signal inversion up into the low-MHz range.
Vce saturation and gain — the numbers that matter for switching
Vce saturation is specified at 300 mV maximum with a base current of 500 µA and collector current of 10 mA. That is a low-drop switch for a 10 mA load — the transistor stays out of deep saturation, which helps switching speed. Minimum DC current gain is 70 at 5 mA collector current and 5 V Vce, so a 100 µA base drive comfortably saturates a 7 mA load. For higher collector currents up to the 100 mA maximum, budget more base drive and expect higher saturation voltage.
Package and storage note
Housed in a PG-SOT23 package (TO-236 / SC-59 compatible), surface-mount only. Ships in Tape & Reel. Maximum power dissipation is 200 mW — keep the junction temperature in check if running near the current limit continuously. Standard MSL handling applies; store the reels dry if the moisture-barrier bag has been opened.