BD678 PNP Darlington Transistor Equivalent & Substitute Parts

Part Overview

The BD678 is a PNP Darlington bipolar junction transistor rated for 60 V collector-emitter breakdown voltage and 4 A maximum collector current. Designed for Through Hole mounting in TO-126 package configuration, this component delivers 40 W maximum power dissipation with a minimum DC current gain of 750 at specified operating conditions.

The onsemi BD678 carries an Obsolete product status. Locating equivalent substitute parts becomes necessary for ongoing production requirements, design updates, and long-term supply chain continuity. Active alternatives with identical electrical specifications and compatible packaging enable seamless integration into existing circuit designs.

Substiute Parts

BD678

onsemiIn Stock: 1307BD678 Datasheet

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BD678

STMicroelectronicsIn Stock: 1259BD678 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the BD678 is determined by strict equivalence across all critical electrical and mechanical parameters. The following parameters establish substitution validity:

Electrical Equivalence Criteria:

• Transistor Type: PNP - Darlington configuration
• Current - Collector (Ic) Max: 4 A
• Voltage - Collector Emitter Breakdown (Max): 60 V
• Vce Saturation (Max) @ Ib, Ic: 2.5V @ 30mA, 1.5A
• Current - Collector Cutoff (Max): 500µA
• DC Current Gain (hFE) Min @ Ic, Vce: 750 @ 1.5A, 3V
• Power - Max: 40 W

Mechanical Compatibility Criteria:

• Mounting Type: Through Hole
• Package / Case: TO-225AA, TO-126-3 or equivalent SOT-32-3

Substitute parts must satisfy all electrical parameters without deviation. Package compatibility is verified through supplier device package designation. Parts meeting these criteria enable direct functional replacement in circuit applications.

Parameter Comparison

Engineering Selection Recommendations

The STMicroelectronics BD678 (SOT-32-3 package) qualifies as a direct electrical and mechanical substitute for the onsemi BD678 (TO-126 package). All critical electrical parameters match exactly across collector current, breakdown voltage, saturation characteristics, cutoff current, and DC current gain specifications.

Product Status Consideration: The onsemi BD678 carries Obsolete designation, indicating discontinued production and limited future availability. The STMicroelectronics BD678 maintains Active product status, ensuring ongoing supply, technical support, and manufacturing continuity.

Compliance Advantage: The STMicroelectronics variant achieves ROHS3 compliance, whereas the onsemi version is RoHS non-compliant. For applications subject to RoHS regulatory requirements or customer specifications mandating RoHS compliance, the STMicroelectronics substitute provides regulatory alignment.

Package Compatibility: Both variants employ Through Hole mounting technology. The TO-126 and SOT-32-3 package designations represent equivalent physical form factors suitable for identical PCB footprints and thermal management configurations.

Selection of the STMicroelectronics BD678 eliminates obsolescence risk while maintaining full electrical equivalence and improving regulatory compliance posture.

Frequently Asked Questions (FAQ)

Q: Can the STMicroelectronics BD678 replace the onsemi BD678 in existing designs?

A: Yes. The STMicroelectronics BD678 satisfies all electrical specifications of the onsemi BD678, including collector current (4 A), breakdown voltage (60 V), saturation characteristics, and DC current gain (750 minimum). Both components employ Through Hole mounting and compatible package configurations.

Q: What is the difference between TO-126 and SOT-32-3 packages?

A: TO-126 and SOT-32-3 represent equivalent Through Hole package designations for three-terminal transistor devices. Both accommodate identical pin configurations and PCB mounting patterns. The package designation difference reflects manufacturer nomenclature variation without affecting functional or mechanical compatibility.

Q: Why is the onsemi BD678 listed as Obsolete?

A: Obsolete status indicates the manufacturer has discontinued production. The component remains available through existing inventory channels but receives no new manufacturing runs. Transition to active alternatives ensures long-term supply security and design continuity.

Q: Does the STMicroelectronics BD678 require circuit modifications?

A: No. Identical electrical parameters across all critical specifications enable direct substitution without circuit redesign, component value changes, or layout modifications.

Q: What is the significance of RoHS3 compliance?

A: ROHS3 compliance certifies the component meets Restriction of Hazardous Substances Directive requirements, restricting lead, cadmium, mercury, and other hazardous materials. Applications subject to RoHS regulations or customer specifications require compliant components. The STMicroelectronics variant satisfies this requirement; the onsemi version does not.

Q: Are thermal characteristics identical between the two variants?

A: Both components specify 40 W maximum power dissipation and operate across compatible temperature ranges. The STMicroelectronics variant specifies 150°C maximum junction temperature; the onsemi variant specifies -55°C to 150°C operating range. Both support equivalent thermal management approaches in circuit applications.

Q: Can I mix onsemi and STMicroelectronics BD678 components in the same production batch?

A: Yes. Electrical equivalence permits interchangeable use. However, maintaining consistent component sourcing from a single manufacturer within a production batch simplifies supply chain management and documentation.