The Infineon BCR523E6433HTMA1 is an NPN pre-biased transistor in a PG-SOT23 surface-mount package. It integrates a bias resistor network — 1 kOhm base resistor (R1) and 10 kOhm emitter-base resistor (R2) — eliminating two external resistors from the bill of materials. This makes it a compact, single-component solution for switching and driver stages where the base drive conditions are fixed. With a 500 mA maximum collector current and 50 V collector-emitter breakdown voltage, it handles moderate loads in low-side switching, relay and solenoid drivers, and logic-level interface circuits. The 100 MHz transition frequency supports switching applications up to several megahertz. The 330 mW power dissipation limit in the SOT-23 package means the part is suited for signal-level and low-to-medium power switching, not continuous high-current loads. The 300 mV saturation voltage at 50 mA (with 2.5 mA base drive) keeps conduction losses modest in saturated switching.
Lifecycle and sourcing reality
This part carries a Last Buy lifecycle status. That means the manufacturer has announced end-of-life, and the final production window is closing. Procurement should treat this as a time-limited sourcing event — once the last-time-buy window closes, availability shifts entirely to the surplus and broker channel.
The 1 kOhm base resistor and 10 kOhm emitter-base resistor set the turn-on threshold and base current for a given input voltage. At a 3.3 V logic drive, the base current is roughly (3.3 V - 0.7 V) / 1 kOhm = 2.6 mA, which is enough to saturate the transistor at collector currents up to about 180 mA (assuming hFE of 70). For the full 500 mA rating, a higher drive voltage or a lower-value R1 variant is needed. The 100 nA collector cutoff current ensures negligible leakage in the off state at room temperature, important for battery-powered circuits where every microamp counts.