Part of the Day · BAV99 — SOT-23 high-speed switching diode (2 in series) (marking A7)

Part of the Day · 2026-10-28

A tiny SOT-23 chip that holds two high-speed switching diodes connected in series. It is especially common in protection circuits: pin 3 goes to the signal line, pin 1 to GND and pin 2 to the supply, keeping the signal clamped within the supply range. The chip is marked A7 plus a one-letter factory code.

Actual size

↓ Actual size, left edge aligned to 0 on the ruler

One ruler tick = 1mm. On PC this is actual size on a 24-inch FHD monitor at 100% zoom; on iPhone it adjusts automatically. For other screens, use “Calibrate ruler” below.

Enlarged (SOT-23 · top view · approx. 20×)

Pins 1 Diode 1 anode (A1) · 2 Diode 2 cathode (K2) · 3 Diode 1 cathode and diode 2 anode (K1, A2)

Package SOT-23 · Marking A7

Key specifications

Values are from the Nexperia datasheet.

Marking and pins

Marking code A7 · Pins 1 Diode 1 anode (A1) · 2 Diode 2 cathode (K2) · 3 Diode 1 cathode and diode 2 anode (K1, A2)

Typical uses

• Input protection — pin 3 to the signal line, pin 1 to GND, pin 2 to the supply, so the signal cannot go beyond the supply range
• High-speed switching · reverse polarity protection · general-purpose switching (datasheet applications)

Companion & similar parts

• BAV70 — Also a dual diode, but a common-cathode type with the cathodes tied together — different pin connections, not a substitute
• BAW56 — Common-anode type with the anodes tied together — also different pin connections
• 1N4148 — Single small-signal switching diode (leaded type)

The Nexperia marking code is A7 followed by a one-letter factory code (A7%). From the 2022 edition it became a single-type data sheet for the non-automotive grade; the automotive grade is sold separately as a -Q part. Other makers may use different marking codes.