Integrated resistor network saves board space
The BCR166 is a PNP pre-biased transistor from Infineon in a SC-70 (SOT-323) surface-mount package. It integrates a 4.7 kΩ base resistor (R1) and a 47 kΩ emitter-base resistor (R2), eliminating two external passives per switching node. This is the part you reach for when you need to drive a low-side load from a microcontroller GPIO without adding resistor pairs to the BOM.
Switching performance and saturation
Collector-emitter breakdown is rated at 50 V, with a maximum continuous collector current of 100 mA and total power dissipation of 250 mW. The 160 MHz transition frequency supports switching into the low-MHz range. Vce saturation is specified at 300 mV maximum with 500 µA base drive and 10 mA collector current — a clean on-state voltage for a 5 V or 3.3 V logic interface. Collector cutoff leakage is held to 100 nA (ICBO), important for battery-powered circuits where off-state current bleeds the rail.
DC gain and drive margin
Minimum DC current gain (hFE) is 70 at 5 mA collector current and 5 V Vce. With the integrated 4.7 kΩ base resistor, a 3.3 V logic output delivering about 0.7 mA base current gives enough drive headroom to saturate the transistor at collector currents up to roughly 50 mA. The 47 kΩ emitter-base resistor ensures the transistor is held off when the GPIO is tri-stated or high-impedance.
Package and marking verification
The BCR166 is supplied in the PG-SOT323-3-1 package (SC-70 / SOT-323 footprint). The supplier device package code is PG-SOT323-3-1. When inspecting incoming material, confirm the top-side laser marking matches Infineon's standard for this date-code lot.