Dual pre-biased NPN/PNP in one SM6 package
The Toshiba RN4601(TE85L,F) integrates one NPN and one PNP pre-biased transistor in a single SM6 surface-mount package, each with 4.7 kΩ base and emitter-base resistors built in. That means two switching channels — one high-side, one low-side — in one tiny SC-74 / SOT-457 footprint, no external bias resistors needed. Collector-emitter breakdown is rated 50 V, continuous collector current 100 mA, and transition frequency 250 MHz, so it handles general-purpose switching and level shifting up to a few tens of MHz without breaking a sweat.
What the 4.7 kΩ bias resistors mean for your BOM
Both the base resistor (R1) and the emitter-base resistor (R2) are 4.7 kΩ on each transistor. That symmetry simplifies the drive calculation: at 5 V logic, base current lands around 1 mA, and the minimum DC current gain of 30 at 10 mA collector current means the output stage saturates reliably. Vce(sat) is only 300 mV at 250 µA base, 5 mA collector — useful when you are switching a relay coil or an LED string and want to keep the voltage drop low.