BD677AS Equivalent & Substitute Parts

Part Overview

The BD677AS is an NPN Darlington bipolar junction transistor manufactured by onsemi, rated for 60 V collector-emitter breakdown voltage and 4 A maximum collector current in a TO-126-3 through-hole package. This device is classified as obsolete, necessitating identification of active equivalent alternatives for ongoing design requirements and procurement needs. Substitute parts must maintain electrical performance within the specified parameter ranges while accommodating potential package variations.

Substiute Parts

BD677AS

onsemiIn Stock: 786BD677AS Datasheet

Current PartRFQ

BD677

STMicroelectronicsIn Stock: 1863BD677 Datasheet

DirectRFQ

BD677A

STMicroelectronicsIn Stock: 2487BD677A Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the BD677AS is determined by equivalence across the following critical electrical parameters: maximum collector current (4 A), collector-emitter breakdown voltage (60 V), maximum power dissipation (40 W), operating temperature range (150°C junction temperature), and DC current gain minimum specification (750 hFE). All substitute parts must maintain NPN Darlington transistor topology and through-hole mounting configuration.

The identified substitute parts—BD677 and BD677A, both manufactured by STMicroelectronics—satisfy these core electrical requirements. Both devices are classified as active products, addressing the obsolescence status of the BD677AS. Package variations exist between the original TO-126-3 specification and the SOT-32-3 supplier device packages of the substitutes; however, both package types are listed within the compatible Package/Case designations (TO-225AA, TO-126-3).

Substitution logic is based strictly on:

• Identical maximum collector current rating (4 A)
• Identical collector-emitter breakdown voltage (60 V)
• Identical maximum power dissipation (40 W)
• Identical operating temperature maximum (150°C)
• Identical DC current gain minimum (750 hFE)
• Identical transistor topology (NPN Darlington)
• Identical mounting type (Through Hole)
• Identical regulatory compliance (ROHS3, REACH Unaffected)

Parameter Comparison

Engineering Selection Recommendations

Both BD677 and BD677A from STMicroelectronics are qualified substitutes for the obsolete BD677AS. Selection between these two alternatives is based on product availability and application-specific saturation voltage requirements.

BD677A demonstrates parameter alignment identical to the BD677AS across all specified electrical characteristics, including Vce saturation (2.8V @ 40mA, 2A) and DC current gain measurement conditions (750 @ 2A, 3V). This part is classified as active with 2443 units in stock.

BD677 provides equivalent electrical performance with a lower saturation voltage specification (2.5V @ 30mA, 1.5A) and DC current gain measurement at reduced collector current (750 @ 1.5A, 3V). This part is classified as active with 1804 units in stock.

Both substitute parts maintain ROHS3 compliance, REACH unaffected status, and identical moisture sensitivity classification (MSL 1 - Unlimited) as the original device. Package variations exist in supplier device packaging (SOT-32-3 versus TO-126-3); however, both are compatible with the specified Package/Case designations.

Frequently Asked Questions (FAQ)

Q: Can BD677 or BD677A directly replace BD677AS in existing designs?

A: Both BD677 and BD677A satisfy the core electrical specifications of the BD677AS: 4 A maximum collector current, 60 V breakdown voltage, 40 W power dissipation, and 750 minimum DC current gain. Direct substitution is supported from an electrical standpoint. Physical package compatibility must be verified against PCB layout requirements, as the supplier device packages differ (SOT-32-3 versus TO-126-3).

Q: What is the difference between BD677 and BD677A?

A: Both devices are NPN Darlington transistors with identical maximum ratings. The primary difference is saturation voltage specification: BD677A matches the BD677AS specification (2.8V @ 40mA, 2A), while BD677 specifies lower saturation voltage (2.5V @ 30mA, 1.5A) at different measurement conditions. DC current gain is measured at 2A for BD677A and 1.5A for BD677.

Q: Are there package compatibility concerns?

A: The BD677AS uses TO-126-3 supplier device package, while both BD677 and BD677A use SOT-32-3 supplier device packages. Both package types are listed within the compatible Package/Case designations (TO-225AA, TO-126-3). Physical pin configuration and lead spacing must be verified against PCB design specifications before implementation.

Q: Do the substitute parts maintain regulatory compliance?

A: Both BD677 and BD677A are ROHS3 compliant and REACH unaffected, matching the compliance status of the BD677AS. Moisture sensitivity level is identical (MSL 1 - Unlimited) across all three parts.

Q: Why is BD677AS classified as obsolete?

A: The BD677AS is listed as obsolete by onsemi. Active alternatives from STMicroelectronics (BD677 and BD677A) provide equivalent electrical performance and are recommended for new designs and ongoing procurement requirements.

Q: What inventory status should influence part selection?

A: BD677A has 2443 units in stock, while BD677 has 1804 units in stock. Both represent adequate inventory for production requirements. Selection should prioritize application-specific saturation voltage requirements and package compatibility with existing PCB designs.