Part of the Day · BC817 — SOT-23 NPN transistor (marking 6D)

Part of the Day · 2026-10-23

An SMD general-purpose NPN transistor that can handle up to 500mA. It is often found switching somewhat larger loads such as relays and LEDs, and is marked 6D 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 Base · 2 Emitter · 3 Collector

Package SOT-23 · Marking 6D

Key specifications

Values are from the Nexperia datasheet.

Marking and pins

Marking code 6D · Pins 1 Base · 2 Emitter · 3 Collector

Typical uses

• General-purpose switching — driver for loads of a few hundred mA such as relays and LEDs
• General-purpose signal amplification

Companion & similar parts

• BC807 — PNP complement (stated in the datasheet) — opposite polarity, not a substitute
• BC817-40 — Gain-grade version of the same BC817 (hFE 250~600, marking code 6C)
• MMBT3904 — Also a SOT-23 NPN, but a smaller 200mA type

The Nexperia marking code is 6D followed by a one-letter factory code (6D%). The -16, -25 and -40 grades use different codes (6A, 6B, 6C), and other makers may use different codes.