What this pre-biased PNP does
The Infineon BCR166WE6327HTSA1 is a PNP pre-biased transistor in a SC-70 SOT-323 package, integrating two bias resistors — a 4.7 kOhm base resistor (R1) and a 47 kOhm base-emitter resistor (R2) — so you can drive it directly from a logic output without adding external resistors. It handles collector currents up to 100 mA and a collector-emitter breakdown voltage of 50 V, with a transition frequency of 160 MHz, making it a fit for low-power switching, relay drivers, and interface level shifting on a surface-mount board.
Infineon lists the BCR166WE6327HTSA1 as obsolete.
Key ratings for the switching decision
The 50 V VCEO rating gives you headroom for 24 V or 48 V industrial rails. The 100 mA continuous collector current covers small relay coils, LED strings, and logic-level translation. Saturation voltage is 300 mV at 500 µA base drive and 10 mA collector current — low enough to keep dissipation in check for a 250 mW package. The minimum DC current gain of 70 at 5 mA, 5 V ensures consistent on-state performance across temperature.