Pre-biased NPN in a SOT-23 — what the integrated resistors mean
The Infineon BCR133E6433HTMA1 is an NPN pre-biased transistor in a PG-SOT23 surface-mount package. It integrates two 10 kOhm resistors — one in series with the base (R1) and one between base and emitter (R2) — eliminating the need for external bias components in low-side switching and driver applications. The transistor is rated for a collector-emitter breakdown voltage of 50 V and a continuous collector current of 100 mA, with a power dissipation ceiling of 200 mW.
NRND status — plan your BOM transition
For new designs, Infineon's current pre-biased transistor portfolio — parts sharing the same SOT-23 footprint and 10 kOhm resistor values — should be evaluated as a form-fit-function replacement.
200 mW power limit and thermal derating
The 200 mW maximum power dissipation is the thermal ceiling for the SOT-23 package. In practice, ambient temperature derating applies — at 85 °C the allowable dissipation drops significantly, so the load current and duty cycle must be checked against the thermal resistance of the board. For continuous 100 mA collector current, the VCE(sat) of 300 mV at 10 mA gives a rough dissipation of 30 mW under saturation, leaving headroom; linear-mode operation at higher VCE will consume the budget quickly.