Diodes Incorporated BC817-40W-7

Overview

BC817-40W-7 from Diodes Incorporated is a 45V, 500mA NPN small-signal transistor in SOT323 package, featuring h_FE = 250–600 at I_C = 100mA/V_CE = 1.0V, V_CE(SAT) ≤ 700mV at I_C = 500mA/I_B = 50mA, and f_T = 100MHz - designed for switching and audio-frequency amplification in space-constrained PCBs.

For engineers reviewing the BC817-40W-7 datasheet, BC817-40W-7 pinout, BC817-40W-7 application, or BC817-40W-7 equivalent, key selection criteria include DC current gain spread (250–600), thermal resistance (625°C/W), AEC-Q101 qualification, SOT323 mechanical compatibility, and complementary PNP pairing with BC807-40W.

Technical Context

This NPN bipolar junction transistor uses epitaxial planar die construction for stable gain and low leakage. It operates across –65°C to +150°C with 4kV HBM ESD rating and meets automotive reliability standards per AEC-Q101.

Its 45V V_CEO, 500mA I_C, and 200mW power dissipation support medium-current digital switching and linear amplification. The 100MHz f_T enables use up to mid-audio frequencies with predictable gain roll-off.

Key Specifications

Pinout & Package

Package: SOT323 - surface-mount plastic case, 2.1mm × 1.3mm × 0.9mm, matte tin-plated leads, moisture sensitivity level 1, UL 94V-0 rated.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN small-signal transistor applications.

Compared with BC817-40W-7, the SOT23 variant trades miniaturization for thermal margin, while MMBT4401LT1G offers higher speed but lacks automotive qualification - making BC817-40W-7 optimal for space-constrained, thermally managed, and automotive-compliant designs.

Availability

BC817-40W-7 is available at Aetrix Electronics and suitable for LED driver circuits, microcontroller GPIO expansion, audio preamplifier stages, and power supply enable switches requiring stable component supply and AEC-Q101 compliance.

Supply support for BC817-40W-7 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design, manufacturing, and sales operations across Asia, Europe, and North America.

The BC817 series belongs to Diodes' general-purpose bipolar transistor product line, engineered for high-reliability switching and amplification in automotive, industrial, and consumer applications where consistent h_FE, low saturation voltage, and compact packaging are critical.

FAQ

What is the maximum continuous collector current for BC817-40W-7 at 70°C ambient?

At T_A = 70°C, the maximum continuous collector current is derated to approximately 375mA. This is calculated using the 200mW power dissipation limit and R_θJA = 625°C/W: P_D = (T_J(max) − T_A) / R_θJA → I_C(max) ≈ √(P_D / R_CE(SAT)), assuming typical V_CE(SAT) of 0.3V at lower currents. Full derating curves are provided in Figure 4 of DS30575.

Is BC817-40W-7 suitable for linear regulator pass transistor applications?

No - BC817-40W-7 is not recommended as a pass transistor in linear regulators due to its limited power dissipation (200mW) and lack of safe operating area (SOA) characterization beyond pulsed conditions. Its design targets switching and low-power amplification, not sustained high-current, high-V_CE operation required in regulator pass elements.

How does the h_FE variation affect biasing in amplifier designs?

The h_FE range of 250–600 at I_C = 100mA means base current must be designed for worst-case minimum gain (250) to ensure saturation or proper active-region bias. Emitter degeneration resistors and voltage-divider bias networks are recommended to stabilize Q-point against h_FE spread and temperature drift, especially in production environments.

Can BC817-40W-7 replace BC847C in existing SOT23 designs?

No direct replacement - BC817-40W-7 uses SOT323 (smaller) versus SOT23, and has different pinout orientation (E-B-C vs. E-C-B). While electrical specs overlap partially, mechanical incompatibility and pin mismatch prevent drop-in substitution. A redesign of footprint and schematic is required for migration.