BAT54A-E3-08 - VISHAY Dual Schottky Diode, Common Anode, 30V/200mA (SOT-23)

What Are the Technical Specifications of BAT54A-E3-08?

The 5ns reverse recovery is effectively zero in most circuits. At 100kHz, that's 0.05% of the period - a standard diode with 4µs trr spends 40% of each cycle in recovery. So why use PN diodes at all? Because Schottky leakage at high temperature can be a dealbreaker.

The 30V V_RRM is the ceiling. Don't push past 24V nominal rails without margin for transients. Leakage at room temp is 2µA at 25V - but double it for every 25°C rise. At 100°C, expect 15–20µA per diode. If your circuit's standby budget is in the nanoamp range, look elsewhere.

BAT54 Family: Which Configuration Do You Need?

BAT54A vs 1N5819: Signal Schottky vs Power Schottky

The BAT54A is a signal-level Schottky - low capacitance, fast switching, tiny current. The 1N5819 is a power Schottky - higher current, higher capacitance, lower VF at load. Use the BAT54A for clamping and protection; use the 1N5819 for rectification.

When Should You Use (and NOT Use) the BAT54A-E3-08?

✅ Use BAT54A-E3-08 when:

• Dual-line reverse polarity protection on signal inputs. Two independent cathodes to two signal lines, shared anode to ground. A negative spike on either line gets clamped to −0.3V. Both lines protected with one SOT-23 footprint.
• Dual-supply monitoring (positive and negative rails). One cathode to +5V, other to −5V, common anode to a sense resistor. The BAT54A steers whichever rail is higher to the sense node - simple, passive, fast.
• GPIO/ADC input clamping (two channels). Each cathode to a separate ADC input, common anode to ground. Protects two input channels from negative transients with one package. For positive clamping, pair with a BAT54C on the same PCB.
• High-side current steering in low-power circuits. When two power sources need to be steered to a common return path, the BAT54A steers without an active controller.
• Small-signal detection and RF mixing. The 10pF junction capacitance and 5ns recovery make the BAT54A usable as a detector or mixer diode at frequencies up to UHF - a niche but real application.

❌ Don't use BAT54A-E3-08 when:

• Power OR-ing between two supplies. You want BAT54C (common cathode), not BAT54A. The BAT54C's shared cathode goes to the load, anodes to each supply. With BAT54A, you'd be OR-ing grounds - rarely what you want.
• Voltage clamping to VCC and GND rails. Use BAT54S (series configuration). Its internal series connection creates a natural clamp: one diode to VCC, one to GND, signal on the middle node.
• Load current above 150mA continuous. The 200mA rating is at 25°C with good PCB copper. At 85°C ambient and minimum copper, derate to ~120mA. For higher current, use SS34 (3A) or 1N5819 (1A).
• Reverse voltage above 24V nominal. The 30V V_RRM is the absolute maximum. A 24V rail with 20% tolerance already hits 28.8V - too close. For 24V+ rails, use BAT46 (100V) or a higher-voltage Schottky.

What Are the Alternatives to BAT54A-E3-08?

BAT54A vs BAT54C - mirror images. Same silicon, wired differently. BAT54A shares anodes; BAT54C shares cathodes. Two reverse-polarity clamps to ground? BAT54A. OR-ing two supplies to one load? BAT54C. Buy the wrong one and your PCB is wrong - there's no software fix for a flipped diode configuration.

What Are the Typical Applications of BAT54A-E3-08?

Dual-channel ADC input protection. Two ADC inputs connect to pins 1 and 3 (cathodes). Pin 2 (common anode) goes to ground. Any negative transient on either channel gets clamped at −0.3V. Two channels protected in one SOT-23 - half the PCB area of two discrete diodes.

Differential signal line clamping. In a differential pair (RS-485, CAN, differential ADC), both lines need identical protection. A single BAT54A clamps both negative excursions of the pair to ground - matched by design, since both diodes are on the same die.

Battery-backed RTC supply steering. Main supply to one cathode, backup battery to the other, common anode to the RTC V_BAT pin. Whichever cathode is higher forward-biases its diode and powers the RTC. At nanoamp-level RTC currents, V_F drops to ~150mV.

SMD rework and PCB space savings. The SOT-23 footprint is 2.9mm × 1.3mm - about half the size of two SOD-123 discretes. For high-density boards (wearables, IoT sensors, smartphone accessories), that's the difference between fitting and not.

Why Buy BAT54A-E3-08 from ICMASS?

VISHAY factory-original, full reel traceability. We source BAT54A-E3-08 directly from VISHAY-authorized channels. Full lot traceability for production buyers - your QA auditor sees the paper trail, not a question mark.

BAT54 family in one shipment. You're probably buying BAT54A, BAT54C, and BAT54S together for different positions on the same board. We stock all three variants so you get one shipment, one customs form, one invoice.

Shenzhen warehouse, same-day dispatch. Orders placed before 15:00 CST ship same day. 3,000-unit reels in stock. Contact us for a same-day quote on your required quantity.

Frequently Asked Questions

Q1: What's the difference between BAT54A, BAT54C, and BAT54S?

A: Internal diode wiring - same silicon, different connections. BAT54A = common anode (pin 2 shared anode, pins 1&3 cathodes). BAT54C = common cathode (pin 2 shared cathode, pins 1&3 anodes). BAT54S = series (pin 2 connects cathode of D1 to anode of D2). Same SOT-23 package. Pick based on which node in your circuit is common.

Q2: Can I use BAT54A for reverse polarity protection?

A: Yes, for signal-level lines up to 30V and 200mA. Connect the cathode to the signal line and the common anode to ground. Negative voltages get clamped to −0.3V. For power supply reverse protection at higher currents, use a series Schottky like the 1N5819 or a P-channel MOSFET ideal diode.

Q3: Why does my BAT54A leak current when reverse-biased?

A: Schottky diodes have inherently higher reverse leakage than silicon PN diodes - and it doubles roughly every 25°C. At 25°C, I_R is ~2µA at 25V. At 85°C, expect 10–20µA. At 125°C, it can reach 100µA or more. If your circuit has a nanoamp standby budget, Schottky leakage will dominate. Consider a silicon diode (BAS16, 25nA leakage) or a MOSFET ideal diode controller.

Q4: Can I put 12V through a BAT54A?

A: Yes - 12V is well within the 30V rating. But check for transients. A 12V automotive rail with load-dump spikes can briefly exceed 30V. Add a TVS diode or series resistor if your supply isn't clean. For sustained 24V rails, consider the BAT46 (100V) instead.

Q5: How much current can the BAT54A really handle?

A: 200mA per diode at 25°C with good PCB copper - derate to ~120mA at 85°C. The 230mW power dissipation is the real limit. At 200mA and 800mV V_F, that's 160mW per diode - fine at room temp. At 85°C ambient, the thermal margin shrinks. For continuous loads above 100mA, add copper pour under the SOT-23 pads.

Q6: BAT54A vs 1N5819 - which one for my circuit?

A: BAT54A for signal protection and clamping (low C, low I). 1N5819 for power rectification (high I, higher C). The BAT54A's 10pF capacitance is invisible at most signal frequencies. The 1N5819's 110pF can roll off a high-speed signal. But the 1N5819 handles 1A - 5× the BAT54A's rating. Match the diode to the job.

Q7: Does the BAT54A need a heatsink?

A: No - at 200mA max, the SOT-23 package dissipates 160mW through the PCB copper. A standard 1oz copper pad under all three pins is sufficient. For high-density boards, ensure at least one pin has a copper pour - don't route all three to thin traces.

Q8: What happens if I exceed 30V reverse on the BAT54A?

A: Avalanche breakdown - the diode conducts in reverse, permanently if current isn't limited. Unlike a Zener, the BAT54A isn't designed for breakdown operation. A single overvoltage event with enough current will destroy the junction. If your circuit can see above 30V - even briefly - add a TVS or pick a higher-voltage part.

Related Products

• BAT54C-E3-08 - Dual Schottky, Common Cathode, same SOT-23
• BAT54S-E3-08 - Dual Schottky, Series Configuration, same SOT-23
• 1N5819HW-7-F - Power Schottky, 40V/1A, SOD-123
• SS34 - Power Schottky, 40V/3A, SMC
• Standard vs Ultrafast vs Schottky - Which Rectifier Do You Need?