BD677A Equivalent & Substitute Parts

Part Overview

The BD677A is an NPN Darlington bipolar junction transistor manufactured by STMicroelectronics, designed for general-purpose switching and amplification applications. This component operates at a maximum collector-emitter voltage of 60 V with a maximum collector current of 4 A and dissipates up to 40 W of power. The device is housed in a SOT-32-3 package for through-hole mounting and maintains an active product status with full availability in inventory.

Substitute parts become necessary when the primary component reaches end-of-life status, experiences supply constraints, or when design requirements permit operation within the electrical and mechanical parameters of alternative devices. The BD675AG represents a viable substitute option with comparable electrical characteristics, though with a reduced maximum voltage rating.

Substiute Parts

BD677A

STMicroelectronicsIn Stock: 2487BD677A Datasheet

Current PartRFQ

BD675AG

onsemiIn Stock: 935BD675AG Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the BD677A with the BD675AG is permissible based on the following electrical and mechanical parameters that remain constant or compatible between the two devices:

Matching Parameters:

• Transistor Type: Both are NPN - Darlington configurations
• Maximum Collector Current (Ic): Both rated at 4 A
• Vce Saturation: Both specified at 2.8 V @ 40mA, 2A
• Collector Cutoff Current: Both at 500 µA maximum
• DC Current Gain (hFE): Both minimum 750 @ 2A, 3V
• Maximum Power Dissipation: Both rated at 40 W
• Mounting Type: Both through-hole configurations
• Package / Case: Both compatible with TO-225AA and TO-126-3 packages
• RoHS Status: Both ROHS3 Compliant
• Moisture Sensitivity Level: Both MSL 1 (Unlimited)

Differing Parameters:

• Voltage - Collector Emitter Breakdown: BD677A rated at 60 V; BD675AG rated at 45 V
• Operating Temperature Range: BD677A specified at 150°C maximum; BD675AG specified at -55°C to 150°C
• Product Status: BD677A is Active; BD675AG is Obsolete
• Manufacturer: BD677A by STMicroelectronics; BD675AG by onsemi

The BD675AG operates within a reduced voltage envelope (45 V versus 60 V), making it suitable for applications where the supply voltage does not exceed 45 V. The extended lower temperature specification of the BD675AG provides additional operational margin in cold environments.

Parameter Comparison

Engineering Selection Recommendations

BD677A Selection Criteria: The BD677A is the primary component choice for new designs and applications requiring a maximum collector-emitter voltage of 60 V. This device maintains active product status with STMicroelectronics, ensuring long-term availability and supply chain stability. The component is ROHS3 compliant and carries unlimited moisture sensitivity classification, suitable for standard manufacturing and storage environments.

BD675AG Selection Criteria: The BD675AG is applicable as a substitute only in applications where the maximum supply voltage does not exceed 45 V. This device is classified as obsolete, indicating discontinued production by onsemi. Selection of the BD675AG is restricted to legacy system maintenance, repair operations, or applications with existing inventory constraints on the primary BD677A component. The extended operating temperature range (-55°C to 150°C) of the BD675AG provides operational advantage in temperature-critical applications within the 45 V voltage constraint.

Both devices maintain identical electrical performance in current handling, gain characteristics, saturation behavior, and power dissipation. Package compatibility and through-hole mounting characteristics are equivalent. Compliance certifications (ROHS3, MSL 1) are identical between both components.

Frequently Asked Questions (FAQ)

Q: Can the BD675AG directly replace the BD677A in all applications?

A: The BD675AG is a direct functional substitute only in applications where the maximum collector-emitter voltage does not exceed 45 V. If the circuit design operates at voltages between 45 V and 60 V, the BD675AG is not suitable. Verify the maximum supply voltage in your circuit design before substitution.

Q: What is the primary difference between these two Darlington transistors?

A: The primary electrical difference is the maximum collector-emitter breakdown voltage: BD677A is rated at 60 V, while BD675AG is rated at 45 V. All other electrical parameters—collector current, saturation voltage, current gain, and power dissipation—are identical. The BD675AG also specifies an extended lower operating temperature limit of -55°C compared to the BD677A.

Q: Are the packages physically identical?

A: Both the BD677A and BD675AG are housed in TO-225AA and TO-126-3 packages for through-hole mounting. The physical dimensions and pin configurations are compatible, allowing direct board-level substitution from a mechanical standpoint.

Q: Why is the BD675AG listed as obsolete?

A: The BD675AG is classified as obsolete by onsemi, indicating that production has been discontinued. This status affects long-term availability and supply chain planning. For new designs, the BD677A is the recommended component due to its active product status with STMicroelectronics.

Q: Are there any compliance or certification differences between these parts?

A: Both the BD677A and BD675AG are ROHS3 compliant and carry MSL 1 (Unlimited) moisture sensitivity classification. Compliance certifications are equivalent between the two devices.

Q: What applications are suitable for the BD675AG substitute?

A: The BD675AG is suitable for legacy system repairs, maintenance operations, or applications with existing inventory of this component. New designs should specify the BD677A. Applications operating at voltages below 45 V may use either component, provided supply availability is confirmed.

Q: How do I verify if my circuit can use the BD675AG?

A: Review your circuit schematic and identify the maximum collector-emitter voltage that the transistor will experience during normal operation and worst-case transient conditions. If this voltage is 45 V or below, the BD675AG is electrically compatible. If the voltage exceeds 45 V, the BD677A must be used.