What Is a Small Signal Schottky Barrier Diode?

Updated: October 28, 2026

A small-signal Schottky barrier diode is optimized for low forward voltage and fast response at milliamp-level currents—clamps, detectors, and high-speed logic paths—not bulk power rectification.

Key Takeaways

• The barrier is a metal-semiconductor junction, so the diode has no minority-carrier storage to clear — recovery is in the nanosecond range rather than the hundreds of nanoseconds a p-n device can need.
• Barrier height is a design choice with two ends: lowering it reduces the forward drop and raises reverse leakage. The datasheet always shows both.
• Reverse voltage is the other limit. Small-signal Schottky parts in these families are rated at 20 V, 30 V or 40 V, well below a p-n switching diode.
• Leakage at temperature is the number that surprises designs: in the BAT54 family the maximum rises from 1 µA at 25 °C to 100 µA at a 100 °C junction.
• Package choice follows the current: a leadless outline for density, a flat-lead power outline when the same function has to carry more.

Three Real Parts, and What Each One Costs

Reading three datasheets side by side shows the trade better than any summary. All three are small-signal Schottky rectifiers; the differences are the barrier, the package and the leakage you accept in exchange for the forward drop.

Parameter	PMEG2005EPK	PMEG4005EJ	BAT54 (ST)
Reverse voltage	20 V	40 V	40 V
Current	0.5 A average	0.5 A average; 7 A repetitive peak (1 ms, δ ≤ 0.25); 10 A non-repetitive (8 ms square)	300 mA continuous; 1.25 A non-repetitive (10 ms sinusoidal)
Forward voltage	360 mV typ, 410 mV max at 500 mA	420 mV typ, 470 mV max at 500 mA	240 mV at 0.1 mA; 400 mV at 10 mA; 900 mV at 100 mA (max)
Reverse leakage	30 µA typ, 130 µA max at 10 V	Per the datasheet curves at the rated voltage	1 µA max at 25 °C; 100 µA max at 100 °C (VR = 30 V)
Recovery / capacitance	3 ns typical recovery	Schottky behaviour; no minority-carrier recovery	7 pF typical, 10 pF max; 5 ns reverse recovery
Package	DFN1608D-2 (SOD1608), 0.37 mm high	SC-90 (SOD323F), 1.7 × 1.25 × 0.7 mm	SO123, SOD323, SOD523, SOT-23, SOT-323
Thermal path	Ceramic-PCB mounting condition for the rated current	Flat-lead body; 360 mW or 830 mW dissipation depending on the pad	500 °C/W junction-to-ambient in SOT-23; 550 in SOT-323/SOD323; 600 in SOD-523

Two rows in that table are the whole argument. Forward drop falls as the barrier is lowered, and leakage rises with it — the 20 V part has the lowest drop and the highest leakage of the three. Reverse voltage is the second: the same technology that makes the diode fast also caps how much voltage it can block, which is why this class stops well short of the 100 V a p-n switching diode offers.

The Calculation That Decides Whether It Fits

Compare the two losses on the same node and the choice usually resolves itself.

• Conduction: at 100 mA, the BAT54 family specifies 900 mV maximum, so the diode dissipates 90 mW. In SOT-23, with the datasheet’s 500 °C/W junction-to-ambient figure, that is a 45 °C rise above ambient.
• Leakage: the same part is specified at 1 µA maximum at 25 °C and 100 µA maximum at 100 °C. At 30 V that hot figure is 3 mW of continuous loss.
• The comparison to make: 3 mW of leakage against 90 mW of conduction loss. On a conducting path the leakage is a rounding error; on a blocking path with no load current, it is the only loss there is.

That is a model assembled from the datasheet’s own maximums with stated assumptions, not a measurement, and the conclusion is the selection rule for the class: small-signal Schottky diodes belong where current flows in the forward direction for a meaningful fraction of the time, and a p-n device belongs where the diode is expected to block and stay quiet — particularly at temperature.

Where They Belong

Low-voltage rectification, reverse-polarity and reverse-current blocking, freewheeling in small converters, and OR-ing of low-voltage rails are the natural duties. The package follows the current and the density: the PMEG2005EPK’s leadless 0.37 mm body is for the smallest boards, while the flat-lead power outline (the CFP15 package used by the 3 A PMEG030V030EPD, qualified to AEC-Q101) is the step up when the same function must carry more current in a slightly thicker part.

Two boundaries are worth stating before a design freezes. High reverse voltage belongs to a different family, and so does any requirement for microamp-level leakage at a high junction temperature. Where either applies, the honest answer is a p-n or wide-bandgap device rather than a Schottky with a lower forward drop.

The small-signal triangle: VF, IR, and capacitance

Low VF helps detection and clamping at small currents; IR and junction capacitance set noise, leakage into high-impedance nodes, and bandwidth. Power Schottky priorities (high IF, package heat) do not transfer unchanged to SOD-323/SOD-523 small-signal parts.

Typical jobs

Signal clamping, peak detection, mixing/RF front-ends (with proper RF parts), and high-speed steering. For amp-level rails, use a power Schottky or other rectifier specified for that current.

Frequently asked questions

Small-signal vs power Schottky?

Current level, capacitance, and package thermal design differ—do not swap them casually.

Why use Schottky for clamps?

Lower VF can limit voltage excursion sooner than a silicon p–n diode.

Does package matter?

Yes—parasitics and pad size affect speed and heat even at small currents.

What to read on the datasheet?

VF at your IF, IR vs temperature, Cj, and absolute maximums.

Related Articles

• What is a SOT-23 switching diode?
• Schottky barrier rectifier selection
• What is a DFN Schottky rectifier?
• Reverse polarity protection diode selection
• Talk to a Good-Ark engineer

Official Resources

• Good-Ark Schottky and rectifier families
• Good-Ark technical documents and datasheets
• Good-Ark package and outline dimensions

References

• Nexperia, PMEG2005EPK — 20 V, 0.5 A low V_F Schottky barrier rectifier — source of the 410 mV maximum forward voltage at 500 mA, 130 µA maximum leakage at 10 V, 3 ns recovery, and the DFN1608D-2 outline 0.37 mm high with its ceramic-PCB current condition. assets.nexperia.com — PMEG2005EPK datasheet (PDF)
• Nexperia, PMEG4005EJ — 40 V, 0.5 A very low V_F MEGA Schottky barrier rectifier — source of the 470 mV maximum forward voltage, the 7 A repetitive peak and 10 A non-repetitive ratings, the SC-90 (SOD323F) dimensions and the 360 mW / 830 mW dissipation figures. assets.nexperia.com — PMEG4005EJ datasheet (PDF)
• STMicroelectronics, BAT54 — Small signal Schottky diodes, DocID5505 Rev 12 — source of the 40 V / 300 mA ratings, the forward voltage at five currents, the leakage at 25 °C and 100 °C, the 7 pF capacitance, 5 ns recovery and the 500 / 550 / 600 °C/W thermal resistances by package. st.com — BAT54 datasheet (PDF)
• Nexperia, PMEG030V030EPD — 30 V, 3 A low V_F MEGA Schottky barrier rectifier — the flat-lead power-outline step-up referenced in the package discussion, with its AEC-Q101 qualification. assets.nexperia.com — PMEG030V030EPD datasheet (PDF)

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