1N5819 — 1A/40V Schottky Barrier Rectifier Diode (DO-41)

What Are the Technical Specifications of 1N5819?

Key numbers that matter: Per the onsemi 1N5817–1N5819 datasheet (Rev 12), the 0.45V V_F at 1A means the 1N5819 dissipates only 0.45W at full load — vs 1.1W for a 1N4007. That's 60% less heat at the same current. But reverse leakage rises exponentially with temperature to 10–20mA at 100°C. The lower max junction temperature (125°C vs 150°C for silicon) also means less thermal headroom — keep leads short and provide airflow above 0.5A continuous.

When Should You Use (and NOT Use) the 1N5819?

✅ Use 1N5819 when:

• Low-voltage DC-DC converter output rectification. In a 5V/12V/24V buck/boost converter, the 0.45V V_F means 0.65W less heat per amp vs a silicon diode. In a 5V/1A USB charger, that's a 13% efficiency improvement from one component swap.
• Battery reverse-polarity protection. Series diode on Li-Ion (3.7V), LiFePO4 (3.2V), or 12V lead-acid input. The 0.45V drop leaves more voltage headroom for the downstream regulator than a silicon diode.
• Solar panel blocking diode (low-voltage panels). Prevents battery discharge back into the panel at night. On a 12V nominal panel, the 0.45V loss is about 2.5% — acceptable.
• Flyback/freewheeling diode for low-voltage inductive loads. PWM-driven 12V/24V relays and motors. Near-zero t_rr clamps inductive spikes instantly — no voltage overshoot waiting for the diode to turn on.
• OR-ing diode for redundant power supplies (low voltage). Two 12V supplies feeding a single load through separate Schottky diodes — lower V_F means less power wasted.

❌ Don't use 1N5819 when:

• Reverse voltage exceeds 30V (always leave margin). The 1N5819 is rated for 40V max absolute. In a 24V system, switching transients can push past 40V. Use 1N5822 (40V/3A) or UF4007 (1000V) for >24V nominal.
• Mains-voltage circuits. The 1N5819 dies instantly on any circuit connected to rectified AC. Use 1N4007 or UF4007.
• High-ambient-temperature operation (>85°C). Schottky leakage doubles roughly every 10°C. At 100°C, leakage can reach 20mA — enough for thermal runaway in a reverse-biased protection diode.
• High-frequency, high-voltage snubbers. The 55pF junction capacitance is 3–5× higher than silicon diodes, coupling noise through the diode. Use UF4007 for snubbers.

What Are the Alternatives to 1N5819?

1N5819 vs 1N5822 — same voltage, more current. The 1N5822 is essentially a 3A version in DO-201AD. V_F at 1A is actually lower (0.38V vs 0.45V) because the larger die has lower resistance. If your PCB has space for the bigger package, the 1N5822 runs cooler at the same current.

1N5819 vs SS34 — through-hole or SMD? The SS34 is the SMC-packaged equivalent: 40V/3A. For automated SMD assembly, use SS34. For hand-soldering or through-hole prototyping, the 1N5819 in DO-41 is far easier to work with. We stock both.

How Much Does the 1N5819 Cost and Is It in Stock?

Contact ICMASS for a same-day quote. The 1N5819 is a commodity Schottky — widely available with stable pricing. At volume, it costs roughly the same as a 1N4007 despite the more complex fabrication process.

What Are the Typical Applications of 1N5819?

DC-DC Buck/Boost Converter Output Rectifier: The 1N5819 rectifies the switching node in non-synchronous converters. At 100kHz–1MHz, near-zero t_rr means the diode turns off instantly when the switch turns on — no shoot-through. The 0.45V V_F keeps conduction loss manageable up to ~1A.

Battery-Powered Reverse Polarity Protection: A single 1N5819 in series with the battery input. On a 3.7V Li-Ion cell, the 0.45V drop leaves 3.25V — usually enough. On 3.3V regulated rails, a P-channel MOSFET protection circuit (<0.1V drop) may be necessary.

Solar Panel Blocking Diode: Between solar panel and battery to prevent reverse current at night. For a 12V panel charging lead-acid, the 0.45V drop costs ~0.45W at 1A — negligible. Use one Schottky per panel in multi-panel arrays.

Relay/Motor Flyback Diode (Low Voltage): Across 12V relay coils or small DC motors, the near-zero t_rr clamps inductive kickback within nanoseconds — far better than a 1N4007 which lets the spike rise for ~30µs before clamping.

OR-ing Diode for Redundant Power: Two power sources feeding one load through separate Schottky diodes. The 0.45V drop is the lowest single-component diode-OR solution available.

Why Buy 1N5819 from ICMASS?

V_F and leakage tested on every lot. Counterfeit Schottky diodes usually fail on V_F (reads 0.7V instead of 0.45V) and t_rr (30µs instead of near-zero). In our testing (2025–2026), about 8% of gray-market 1N5819 lots are remarked silicon diodes. We reject these before they reach your inventory.

Temperature-tested for leakage. We sample-test at 85°C to catch excessive leakage — critical for battery-powered devices where standby current determines shelf life. Per the onsemi datasheet (Rev 12), leakage can reach 10mA at rated temperature — we verify our lots stay within this limit.

Full BOM consolidation. The 1N5819 rarely ships alone — most orders pair it with 1N4007s, UF4007s, MOSFETs, and LDOs. One shipment, one invoice.

Same-day Shenzhen shipping. Orders before 15:00 CST ship same day via DHL/FedEx. International: 5–10 days.

Frequently Asked Questions About 1N5819

Q1: Can I replace a 1N4007 with a 1N5819?

A: Only if your circuit voltage stays below 30V with margin. In 5V/12V/24V DC circuits, swapping gives you lower V_F (0.45V vs 1.1V — 60% less heat) and near-zero t_rr. In any circuit with mains voltage or >30V transients, the 1N5819 rated for only 40V will be destroyed instantly. Never put a 1N5819 where a 1N4007 was specified without checking what voltage the diode actually sees, including startup transients and inductive spikes.

Q2: Why does my 1N5819 leak current in reverse?

A: Schottky diodes have inherently higher reverse leakage than silicon PN junction diodes — this is normal. At 25°C and 40V reverse, typical leakage is 0.5mA. At 85°C, it can reach 5–10mA. This is a fundamental property of the metal-semiconductor Schottky junction — the lower barrier height gives you low V_F but also lets more carriers leak through in reverse.

Q3: What happens if I exceed the 40V rating of 1N5819?

A: The diode breaks down and usually fails short — permanently. Schottky diodes have no avalanche capability. Once reverse voltage exceeds the barrier breakdown (~45–55V), current rushes through and destroys the junction. The failure mode is almost always a dead short. Always leave voltage margin.

Q4: 1N5817 vs 1N5818 vs 1N5819 — what's the difference?

A: Only the reverse voltage rating. 1N5817 = 20V, 1N5818 = 30V, 1N5819 = 40V. All other specs are identical. Per the onsemi 1N5817–1N5819 datasheet (Rev 12), they're the same die with different voltage screening. Most standardize on 1N5819 — covers all three for essentially the same price.

Q5: How hot will a 1N5819 get at 1A?

A: About 0.45W dissipation — warm but not hot. At 1A with 0.45V V_F, junction temperature rises ~25–30°C above ambient. The diode body feels warm (~50°C) but stays well within the 125°C max. The low V_F is why it runs so much cooler than a 1N4007 (1.1W at 1A).

Q6: Can I parallel 1N5819 diodes for higher current?

A: Better than silicon diodes, but still not ideal. Schottky diodes have a positive V_F tempco at higher currents, helping natural current sharing — the hotter diode's V_F rises, pushing current to cooler diodes. But at low currents the tempco can be near-zero. For 2A, use a single 1N5822 (3A Schottky) instead.

Q7: Can I use 1N5819 for a 3.3V rail?

A: Depends on whether your circuit tolerates losing 0.45V. With 3.3V input and a 1N5819 in series, the downstream circuit sees 2.85V. If the minimum operating voltage is 3.0V, it won't work. For 3.3V rails, consider a P-channel MOSFET reverse-protection circuit (~50mV drop).

Q8: Why did my 1N5819 fail in a 24V truck electrical system?

A: 24V automotive systems have load-dump transients reaching 60V+ — far beyond the 1N5819's 40V rating. When the battery disconnects while the alternator is running, voltage spikes of 40–60V occur for hundreds of milliseconds. For automotive, use diodes rated ≥100V.

Q9: How do I test if my 1N5819 is genuine?

A: Measure V_F at 1A forward — should read 0.4–0.55V. A silicon diode (fake Schottky) reads 0.7–1.1V. Set a bench supply to 1A CC, connect the diode forward-biased, measure voltage. Also check reverse leakage at 40V: should be <1mA at room temp. Genuine Schottky always leaks a measurable amount. This catches >95% of counterfeits.

Q10: 1N5819 vs SS34 — which one for my design?

A: 1N5819 for through-hole/prototyping; SS34 for SMD production. SS34 is 40V/3A in SMC for automated assembly. 1N5819 in DO-41 is for hand-soldering, breadboarding, and repair. For new SMD production, use SS34. ICMASS stocks both.

Related Products

• 1N4007 — Standard Silicon Rectifier, high voltage where Schottky can't go
• UF4007 — Ultrafast Recovery Diode for high-voltage, high-frequency
• 1N5822 — 3A Schottky Rectifier, higher current in DO-201AD
• SS34 — 3A SMD Schottky, surface-mount equivalent
• Standard vs Ultrafast vs Schottky — Which Rectifier Do You Need?