BAT54C

The BAT54C from Nexperia is a dual common-cathode Schottky barrier diode in the industry-standard SOT-23 surface-mount package. It is one of the most widely used small-signal Schottky diodes, with extensive multi-source availability from Nexperia, Diodes Inc, onsemi, STMicroelectronics, and others.

The BAT54 series includes three configurations: BAT54 (series pair), BAT54A (common anode), and BAT54C (common cathode). The common-cathode BAT54C connects the cathodes of both diodes to pin 3 (K1,K2), with anodes on pins 1 (A1) and 2 (A2). This configuration is ideal for OR-ing applications, voltage clamping, and reverse polarity protection.

The planar Schottky barrier construction with integrated guard ring provides robust stress protection while maintaining low forward voltage. At 1 mA forward current, the typical Vf is only 240 mV (320 mV at 10 mA, 500 mV at 30 mA), making the BAT54C suitable for low-voltage signal clamping where silicon PN junction diodes would introduce excessive voltage drop.

The 5 ns reverse recovery time and 10 pF junction capacitance enable ultra-high-speed switching applications. The 2 uA maximum reverse leakage at 25 V and 25C is very low for a Schottky diode, important for battery-powered applications where leakage current directly impacts battery life.

The BAT54C is AEC-Q101 qualified, making it suitable for automotive applications. The SOT-23 package is rated for 250 mW total power dissipation at 25C ambient on a standard FR4 PCB footprint. The 600 mA non-repetitive peak forward surge current rating provides margin for transient events.

With 362K+ units in stock at Newark and a unit price of $0.023, the BAT54C is one of the most cost-effective and readily available dual Schottky diodes in the market.

**Schottky Barrier Junction:** Unlike conventional PN junction diodes, Schottky diodes use a metal-semiconductor (metal-silicon) junction. The metal (typically platinum or chromium silicide) forms a rectifying contact with the N-type silicon. Forward bias reduces the Schottky barrier height, allowing majority carriers (electrons) to flow from the semiconductor into the metal with minimal voltage drop. Because conduction involves only majority carriers, there is no minority carrier storage, resulting in near-zero reverse recovery time.

**Guard Ring:** The integrated P-type guard ring surrounding the Schottky junction serves two purposes: it protects the edge of the metal-semiconductor contact from voltage stress that could cause premature breakdown, and it provides controlled avalanche breakdown behavior. The BAT54C breakdown occurs at the guard ring at approximately 30-40 V, well above the rated 30 V reverse voltage.

**Common-Cathode Configuration:** Both diodes share a single cathode connection (pin 3). Current flows from each anode (pins 1 and 2) to the common cathode. In a typical OR-ing application, two power sources connect to the anodes, and the cathode connects to the load. The source with the higher voltage forward-biases its diode and powers the load while the other diode is reverse-biased.

**Fast Recovery:** The 5 ns reverse recovery time is a consequence of majority-carrier conduction. When the diode switches from forward to reverse bias, there are no stored minority carriers to recombine. The apparent recovery time comes from junction capacitance discharge, which is very fast (10 pF x typical circuit impedance).