Obsolete — sourcing this PNP transistor now
The Infineon BC 856B E6433 is listed as obsolete by the manufacturer.
With a 65 V collector-emitter breakdown voltage and 100 mA maximum collector current, this transistor suits general-purpose switching and amplification in circuits up to about 48 V rails with derating. The 330 mW power limit in the SOT-23 package means continuous dissipation needs checking against the operating current and ambient temperature — at 25 °C ambient and 100 mA, VCE must stay under about 3.3 V to stay inside the power budget. The 250 MHz transition frequency gives enough bandwidth for audio amplifiers, signal conditioning, and moderate-speed switching up to a few MHz.
DC gain and saturation — the B-grade selection
The B-grade suffix selects a minimum DC current gain (hFE) of 220 at 2 mA collector current and 5 V VCE. This is the medium-gain bin in the BC 856 family, offering a good balance between consistent drive capability and low saturation voltage — 650 mV maximum at 5 mA base current and 100 mA collector current. The 15 nA maximum collector cutoff current (ICBO) keeps leakage low in high-impedance nodes, which matters for battery-powered or temperature-sensitive designs.
SOT-23 footprint and tape-and-reel delivery
The transistor comes in the standard TO-236-3 / SC-59 / SOT-23-3 surface-mount package, supplier device package PG-SOT23. The Tape & Reel (TR) packaging format suits automated pick-and-place assembly. The 150 °C maximum junction temperature rating allows operation in warm environments, but the 330 mW power limit in this small package means thermal design — not the junction temperature — is the practical constraint for continuous operation.