Pre-biased NPN — one component replaces three
The Infineon BCR133TE6327 is an NPN pre-biased transistor in a SOT-23-3 package. It integrates a 10 kΩ base resistor (R1) and a 10 kΩ emitter-base resistor (R2) on-chip, so a single part replaces the transistor plus two external resistors in a common-emitter switching circuit. Collector-emitter breakdown is rated at 50 V, continuous collector current at 100 mA, and the transition frequency is 130 MHz — enough for low-speed switching up to a few megahertz.
Package and mounting
With 500 µA base drive and 10 mA collector current, Vce(sat) max is 300 mV. That is a clean on-state voltage for a 5 V or 3.3 V logic-level load — the transistor will not eat into the rail margin. The minimum DC current gain of 30 at 5 mA, 5 V means the base drive needs to be about 3% of the load current to guarantee saturation. For a 100 mA load, plan on at least 3.3 mA into the base resistor.
Leakage and cutoff — 100 nA max ICBO
Collector cutoff current is specified at 100 nA maximum (ICBO). That is low enough for most battery-powered or high-impedance nodes — a pulled-up digital input will not drift. If the application is sensitive to sub-microamp leakage, this part holds the line.
