SOD-123 Switching Diode: Fast, Reliable Signal Control for Compact Electronics

Updated: October 28, 2026

SOD-123 houses many switching diodes used for fast signal control in compact layouts. The outline affects footprint and parasitics; speed and voltage still come from the die ratings on the datasheet.

Key Takeaways

• The switching performance belongs to the die, not the outline. In the BAS16 series the electrical ratings are shared while the package varies across seven outlines.
• What the package changes is board area, profile, assembly method and thermal path — and therefore how much continuous current the part can carry.
• Switching diodes in this class are characterised by reverse recovery time and junction capacitance, and the numbers come with test conditions attached.
• Reverse voltage for the family is typically 100 V, which places it in signal and low-voltage power paths rather than mains rectification.
• Automotive programmes can use the same family: the BAS16 series is AEC-Q101 qualified.

What SOD-123 Is, and What It Is Not

SOD-123 is a small-outline surface-mount package for diodes: a two-terminal body sized for automated placement on dense boards. It is not a performance specification.

The Nexperia BAS16 series is the clearest demonstration of that. One datasheet covers seven package variants — SOT23 (TO-236AB), SOD123F (the flat-lead member of the SOD-123 family), SOD323F, the leadless SOD882, SOT416, SOT666 in a triple-isolated configuration, SOT363, SOT323, SOD323 and SOD523 — with shared electrical characteristics: reverse voltage up to 100 V, repetitive peak reverse voltage up to 100 V, reverse recovery time of 4 ns, low capacitance and low leakage, and AEC-Q101 qualification across the family.

What the outline changes	What it does not change
Board area and profile height	Reverse voltage rating
Assembly method and placement density	Reverse recovery time (a stated 4 ns in this family)
Thermal path into the board, and therefore usable continuous current	Junction capacitance class
Parasitic inductance added to the circuit	Leakage specification
Availability of a leadless variant for the smallest designs	Automotive qualification, where the family carries it

The Two Numbers That Decide a Switching Diode

Speed in this device class is described by reverse recovery time and capacitance, and both need their test conditions.

The Nexperia BAV99 series states its switching figure with the measurement attached: a reverse recovery time of 4 ns or less when switched from a forward current of 10 mA to a reverse current of 10 mA through a 100 Ω load, measured at a reverse current of 1 mA. It also quotes a junction capacitance of 1.5 pF or less, a reverse voltage of 100 V, a reverse current of 0.5 µA or less at 80 V, and AEC-Q101 qualification, in SOT23, SOT363 and SOT323 outlines for the dual and quadruple configurations.

That pairing is what the selection turns on. Capacitance loads the signal path and slows the edges it is meant to pass; recovery time determines how long the diode keeps conducting after the voltage reverses. A part with a fast recovery time and a few picofarads is a signal diode; a part with a low forward drop and a much larger reverse leakage is a rectifier. The BAS16 and BAV99 families sit in the first category, which is why they appear in clamping, steering, logic-level shifting and general-purpose switching rather than in a power conversion stage.

Choosing Between the Outlines

Once the electrical part of the specification is fixed, the outline decision is mechanical and thermal.

SOD-123 — and its flat-lead relative SOD123F — is a sensible default for a board that wants a hand-solderable two-terminal part with a reasonable pad size and a footprint that automated placement handles well. SOT23 is the choice when two diodes in one package, or a common three-terminal configuration, saves placement. SOD323 and SOD523 are for the smallest consumer designs, and the leadless SOD882 exists for boards where even that is too large. The honest comparison is area and thermal path against ease of assembly and inspection, because the electrical performance travels with the silicon across all of them.

One boundary condition belongs in the same review: reverse voltage. The 100 V class covers low-voltage rails, signal lines and the control side of a power supply. It does not cover mains rectification or a high-voltage DC bus, where a different device class — a general-purpose or fast-recovery rectifier — applies.

SOD-123 among small diode packages

SOD-123 is larger than SOD-523/SOD-323 but smaller than SOD-123FL or SMA power outlines. Same die families sometimes appear across SOT-23 and SOD-123 (for example BAS16-class switches)—compare trr, Cj, and VR, not only the package drawing.

What “switching diode” should mean on the PDF

Look for reverse-recovery or switching time, capacitance, and leakage at temperature. A part sold as “fast” without conditions is incomplete for timing-critical designs.

Frequently asked questions

What is a SOD-123 switching diode?

A small SMT diode package commonly used for high-speed signal switching and clamping.

Is SOD-123 always a fast diode?

No. Read trr/Cj for the specific MPN.

SOD-123 vs SOT-23?

Different outlines; electrical twins may exist across packages—compare datasheets.

Power rectification?

Usually not—these are signal-class parts unless explicitly power-rated.

Related Articles

• High-speed switching diodes and fast recovery
• What is a SOT-23 switching diode?
• Small-signal diodes and switching speed
• What is a high-speed driver?
• Talk to a Good-Ark engineer

Official Resources

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

References

• Nexperia, BAS16 series — High-speed switching diodes — source of the seven-outline package family (SOT23, SOD123F, SOD323F, SOD882, SOT416, SOT666, SOT363, SOT323, SOD323, SOD523), the 100 V reverse and repetitive peak reverse voltage ratings, the 4 ns reverse recovery time, and the AEC-Q101 qualification statement. assets.nexperia.com — BAS16 series datasheet (PDF)
• Nexperia, BAV99 series — High-speed switching diodes — source of the 4 ns reverse recovery time with its test conditions, the 1.5 pF maximum junction capacitance, 100 V reverse voltage, 0.5 µA maximum reverse current at 80 V, the SOT23/SOT363/SOT323 package options and AEC-Q101 qualification. assets.nexperia.com — BAV99 series datasheet (PDF)
• Nexperia, BZT52 series — Voltage regulator diodes — package-thermal reference for SOD123 in a neighbouring diode family, including the 350 mW standard-footprint and 590 mW one-square-centimetre pad conditions. assets.nexperia.com — BZT52 series datasheet (PDF)

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