BD159 Equivalent & Substitute Parts

Part Overview

The BD159 is an NPN bipolar junction transistor manufactured by onsemi, rated for 350 V collector-emitter breakdown voltage and 500 mA maximum collector current in a TO-126 through-hole package. This device is classified as obsolete, making equivalent substitutes necessary for ongoing production and maintenance applications. The BD159 delivers 20 W maximum power dissipation with a minimum DC current gain of 30 at 50 mA collector current and 10 V collector-emitter voltage, suitable for general-purpose switching and amplification circuits operating across a temperature range of -65°C to 150°C.

Substiute Parts

BD159

onsemiIn Stock: 704BD159 Datasheet

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MJE340

NTE Electronics, IncIn Stock: 2035MJE340 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the BD159 is determined by electrical and mechanical compatibility across the following critical parameters:

Electrical Compatibility Criteria:

• Transistor type must be NPN
• Maximum collector current must equal or exceed 500 mA
• Maximum collector-emitter breakdown voltage must equal or exceed 350 V
• DC current gain (hFE) minimum must equal or exceed 30 at the specified test conditions
• Maximum power dissipation must equal or exceed 20 W

Mechanical Compatibility Criteria:

• Mounting type must be through-hole
• Package must be TO-126-3 or equivalent TO-225AA footprint

The MJE340 meets the electrical requirements for collector current and power dissipation but operates at a reduced maximum collector-emitter breakdown voltage of 300 V. This represents a voltage derating that restricts application scope to circuits operating below 300 V. The DC current gain and collector current specifications remain equivalent to the BD159.

Parameter Comparison

Engineering Selection Recommendations

For Direct Substitution (Voltage ≤ 300 V Applications): The MJE340 serves as a direct electrical and mechanical substitute for the BD159 in applications where the maximum operating voltage does not exceed 300 V. The MJE340 maintains identical collector current, power dissipation, and DC current gain specifications. The MJE340 is currently in active production status, ensuring long-term availability compared to the obsolete BD159.

For Applications Requiring 350 V Rating: Applications requiring the full 350 V collector-emitter breakdown voltage rating of the BD159 cannot use the MJE340 without circuit redesign or voltage derating. Alternative devices with equivalent 350 V ratings must be evaluated from other manufacturers.

Compliance Considerations: Both the BD159 and MJE340 are RoHS non-compliant and carry identical ECCN (EAR99) and HTSUS (8541.29.0095) classifications. Selection between these devices should account for compliance requirements in the target application environment.

Frequently Asked Questions (FAQ)

Q: Can the MJE340 replace the BD159 in all applications? A: The MJE340 is electrically and mechanically compatible with the BD159 only in applications where the maximum operating voltage does not exceed 300 V. The BD159 is rated for 350 V maximum collector-emitter breakdown voltage, while the MJE340 is rated for 300 V. Circuits designed to operate at voltages between 300 V and 350 V require alternative substitutes.

Q: Are the DC current gain specifications identical between these devices? A: Yes. Both the BD159 and MJE340 specify a minimum DC current gain (hFE) of 30 at 50 mA collector current and 10 V collector-emitter voltage. This parameter is matched between the two devices.

Q: Do these transistors use the same physical package? A: Yes. Both devices use the TO-126-3 package with through-hole mounting. The physical footprint and pin configuration are identical, allowing direct PCB mounting compatibility.

Q: What is the primary reason to substitute the BD159? A: The BD159 is classified as obsolete. The MJE340 is in active production, providing assured long-term availability and supply chain continuity for new designs and production runs.

Q: Are there compliance differences between the BD159 and MJE340? A: Both devices share identical RoHS status (non-compliant), ECCN classification (EAR99), and HTSUS code (8541.29.0095). No compliance advantage exists between these two devices.

Q: What collector current and power dissipation specifications apply to both devices? A: Both the BD159 and MJE340 are rated for 500 mA maximum collector current and 20 W maximum power dissipation. These specifications are fully matched.