The Infineon BAS40-04B5003 is a dual Schottky diode in a series-connected configuration, housed in a standard SOT-23-3 surface-mount package. It is rated for a maximum reverse voltage of 40 V and delivers 120 mA of average rectified current per diode. The forward voltage is specified at 1 V maximum when conducting 40 mA, which is typical for a small-signal Schottky. This part is qualified to AEC-Q101, making it suitable for automotive under-hood and cabin electronics, as well as industrial control, power supply OR-ing, and high-speed switching where fast recovery and low forward drop matter.
40 V reverse voltage and 120 mA — what that buys you
The 40 V reverse voltage gives you headroom for clamping 12 V and 24 V automotive rails, while the 120 mA per diode handles signal-level loads like relay coil suppression, logic-level translation, and protection clamps on sensor inputs. The series configuration (cathode of one diode to anode of the other) lets you build a voltage doubler or a bidirectional clamp in one package, saving board space over two discrete SOT-23s.
AEC-Q101 and junction temperature
AEC-Q101 qualification means this diode has passed automotive-grade stress tests including HBM ESD, temperature cycling, and high-temperature reverse bias. The junction is rated to 150 °C, so it can sit next to a hot regulator or in an engine-bay environment without derating concerns. The active lifecycle status means Infineon is still manufacturing this part — no last-time-buy risk for production runs.
SOT-23-3 — field-swappable footprint
The SOT-23-3 package (also known as TO-236-3 or SC-59) is one of the most common three-pin surface-mount footprints. It is easy to hand-solder with a fine-tip iron, and the part marking is usually legible under a loupe. No hot-air station needed for rework — a field swap is straightforward if you have tweezers and a steady hand.