BU810 Equivalent & Substitute Parts

Part Overview

The BU810 is an NPN Darlington bipolar junction transistor manufactured by STMicroelectronics, designed for high-voltage switching applications. This device features a 400 V collector-emitter breakdown voltage rating and 7 A maximum collector current capability in a TO-220-3 through-hole package. The BU810 is classified as obsolete, making identification of functionally equivalent substitute components necessary for ongoing design support, maintenance, and production continuity.

Substiute Parts

BU810

STMicroelectronicsIn Stock: 1477BU810 Datasheet

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MJE5742G

onsemiIn Stock: 8370MJE5742G Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the BU810 is based on strict equivalence of the following critical electrical and mechanical parameters:

Voltage Rating: Both the main part and substitute must maintain a 400 V collector-emitter breakdown voltage to ensure safe operation in the same circuit topology.

Transistor Architecture: Both must be NPN Darlington configurations to preserve base-drive characteristics and switching behavior.

Package Type: Both must use TO-220-3 through-hole packaging to ensure mechanical and thermal compatibility with existing PCB layouts and heatsinking arrangements.

Current Capability: The substitute must support the required collector current range. The BU810 specifies 7 A maximum; substitutes with equal or greater current ratings are acceptable.

Saturation Voltage: The Vce saturation specification determines switching losses and thermal performance. Substitutes must operate within acceptable saturation parameters for the application.

Compliance Standards: Both parts must maintain ROHS3 compliance and REACH unaffected status to satisfy regulatory requirements.

The MJE5742G meets all these criteria and is classified as an active product, providing long-term availability and supply chain stability.

Parameter Comparison

Engineering Selection Recommendations

The MJE5742G is a direct functional substitute for the BU810 in applications requiring NPN Darlington switching at 400 V and up to 7 A collector current. Both devices share identical voltage ratings, package geometry, and regulatory compliance status.

The MJE5742G carries active product status from onsemi, ensuring continued availability, technical support, and supply chain reliability. The BU810, classified as obsolete, presents long-term sourcing risk and limited manufacturer support.

The MJE5742G exhibits a higher maximum collector current rating (8 A versus 7 A), providing additional design margin in current-limited applications. The substitute's operating temperature range extends to −65°C, offering broader environmental compatibility compared to the BU810's 0°C to 150°C implied range.

Both devices maintain ROHS3 compliance and REACH unaffected status, satisfying regulatory requirements for new designs and legacy system maintenance.

Frequently Asked Questions (FAQ)

Q: Can the MJE5742G directly replace the BU810 in existing circuit designs?

A: Yes. Both devices are NPN Darlington transistors in TO-220-3 packages with identical 400 V voltage ratings and compatible saturation characteristics. Pin configuration and thermal properties are equivalent, enabling direct substitution without circuit modification.

Q: What is the significance of the higher current rating on the MJE5742G?

A: The MJE5742G is rated for 8 A maximum collector current compared to the BU810's 7 A. This higher rating provides additional design margin and allows the substitute to handle transient current spikes without exceeding absolute maximum ratings. Applications operating at or near 7 A benefit from this increased headroom.

Q: Are there thermal considerations when substituting these parts?

A: Both devices use the TO-220-3 package, which provides identical thermal interface characteristics. Heatsinking requirements depend on application power dissipation. The BU810 specifies 75 W maximum power dissipation; the MJE5742G specifies 2 W. Thermal design must account for actual circuit operating conditions rather than absolute maximum ratings.

Q: Does the MJE5742G's wider operating temperature range affect substitution suitability?

A: The MJE5742G's −65°C to 150°C operating range encompasses the BU810's operating temperature. This extended range does not compromise substitution compatibility and may provide additional environmental flexibility for applications requiring low-temperature operation.

Q: What compliance advantages does the MJE5742G offer?

A: Both parts maintain ROHS3 compliance and REACH unaffected status. The MJE5742G's active product status ensures ongoing compliance updates and regulatory support from onsemi, whereas the BU810's obsolete classification limits manufacturer support for future regulatory changes.

Q: Are there packaging or supplier considerations for the MJE5742G?

A: The MJE5742G is supplied in tube packaging by onsemi, whereas the BU810 packaging format is not specified in available data. Both use identical TO-220-3 case geometry. Tube packaging is standard for active production components and does not affect electrical or mechanical compatibility.