onsemi BD675

Overview

BD675 from onsemi is a plastic medium-power silicon NPN Darlington transistor designed for complementary general-purpose amplifier output stages, with V_CEO = 45 V, I_C = 4.0 A, P_D = 40 W at T_C = 25°C, h_FE ≥ 750 (IC = 1.5 A), and TO-225 package. It serves as a high-gain switching or linear output device in audio amplifiers and power control circuits.

For engineers reviewing the BD675 datasheet, pinout, applications, or equivalent options, key selection factors include its 45 V V_CEO, 4 A continuous collector current capability, Darlington architecture enabling low base drive requirements, thermal resistance of 3.13°C/W (junction-to-case), and Pb-free TO-225 packaging compliant with RoHS.

Technical Context

The BD675 integrates two NPN transistors monolithically in a Darlington configuration, delivering high DC current gain while maintaining single-package simplicity. Its structure enables low base current drive (I_B ≤ 1.0 A) to switch up to 4.0 A collector current, with V_CE(sat) ≤ 2.5 V under specified test conditions.

Rated for operation from –55°C to +150°C junction temperature, the device features complementary pairing with onsemi's BD676 series PNP Darlingtons and shares pinout compatibility across the BD675/677/679/681 family. Thermal derating begins above 25°C at 0.32 W/°C, and safe operating area is constrained by both bonding wire limits and secondary breakdown.

Key Specifications

Pinout & Package

BD675 is housed in a TO-225 package (Case 77-09, Style 1), featuring three electrically distinct terminals with pins 2 and 4 internally connected to the collector. The package includes a metal tab (pin 4 backside) that is electrically connected to the collector and intended for heatsink mounting.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN Darlington transistor applications.

Compared with BD675, MJE800 offers higher voltage rating but same thermal and gain behavior, while BD677G provides a seamless pin-compatible upgrade path with +15 V V_CEO headroom-both retain identical TO-225 mechanical fit and driver interface requirements.

Availability

BD675 is available at Aetrix Electronics and suitable for audio amplifier output stages, DC motor drivers, relay/solenoid interfaces, and linear regulator pass elements requiring stable component supply and legacy-design continuity.

Supply support for BD675 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BD675 belongs to onsemi's legacy medium-power discrete transistor portfolio, engineered specifically for robust, cost-effective linear and switching output stages in industrial and audio equipment where high DC gain and thermal reliability are critical.

FAQ

What is the maximum collector-emitter voltage rating for BD675?

The BD675 has a maximum collector-emitter voltage (V_CEO) rating of 45 V DC. This value is confirmed in the Absolute Maximum Ratings table of the official onsemi datasheet (Rev. 16, November 2024). Exceeding this voltage risks avalanche breakdown and permanent device failure. Designers must ensure worst-case V_CE in their circuit-including transients and inductive spikes-remains below 45 V. The BD675G variant maintains this rating under all specified operating conditions.

Is BD675 pin-compatible with other devices in the BD6xx family?

Yes, BD675 uses the TO-225 package (Case 77-09, Style 1) with standardized pinout: Pin 1 = Emitter, Pins 2 & 4 = Collector (internally tied), Pin 3 = Base. This matches BD677G, BD679G, BD681G, and all "A" variants. Mechanical and electrical pin compatibility enables drop-in substitution within the same voltage class, though V_CEO and thermal performance differ across the family. Always verify voltage and power requirements before replacement.

Does BD675 require a heatsink in normal operation?

Yes, BD675 requires a heatsink for reliable operation beyond brief intermittent use. With R_θJC = 3.13°C/W and P_D = 40 W at T_C = 25°C, even moderate dissipation (e.g., 10 W) raises junction temperature significantly above ambient. Without heatsinking, junction temperature can exceed 150°C at <5 W. A properly sized aluminum heatsink with thermal interface material is mandatory for continuous 4 A operation or any sustained power dissipation above 2 W.

What is the DC current gain (h_FE) specification for BD675?

The BD675 guarantees a minimum DC current gain (h_FE) of 750 at I_C = 1.5 A and V_CE = 3.0 V, per the Electrical Characteristics table. This high gain is intrinsic to its monolithic Darlington structure and enables efficient base drive-e.g., ~2 mA base current suffices for 1.5 A collector current. Note that h_FE decreases at higher currents and temperatures; design margins should account for typical spread and derating.

Is BD675 suitable for switching applications?

Yes, BD675 is suitable for medium-speed switching applications such as relay drivers, PWM motor control, and power supply pass elements. Its Darlington configuration provides fast turn-on with low base drive but introduces slower turn-off due to stored charge; typical switching frequencies are limited to <10 kHz. For higher-frequency switching, consider adding a Baker clamp or base-turnoff assist circuit. Always observe SOA curves and avoid secondary breakdown during inductive switching transitions.