BD743A-S Equivalent & Substitute Parts

Part Overview

The BD743A-S is an NPN bipolar junction transistor manufactured by Bourns Inc., rated for 60 V collector-emitter breakdown voltage and 15 A maximum collector current in a TO-220-3 through-hole package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. The BD743A-S delivers 2 W maximum power dissipation and operates across a temperature range of -65°C to 150°C junction temperature.

Key Parameters

Parameter	Value
Transistor Type	NPN
Voltage - Collector Emitter Breakdown (Max)	60 V
Current - Collector (Ic) (Max)	15 A
Power - Max	2 W
Vce Saturation (Max) @ Ib, Ic	3 V @ 5 A, 15 A
DC Current Gain (hFE) (Min) @ Ic, Vce	20 @ 5 A, 4 V
Operating Temperature	-65°C ~ 150°C (TJ)
Package / Case	TO-220-3
Mounting Type	Through Hole
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the BD743A-S is determined by matching the following critical electrical and mechanical parameters:

Primary Matching Criteria:

Transistor Type: NPN
Voltage - Collector Emitter Breakdown (Max): 60 V minimum
Current - Collector (Ic) (Max): 15 A minimum
Package / Case: TO-220-3
Mounting Type: Through Hole
Operating Temperature Range: -65°C to 150°C (TJ)

Secondary Compatibility Factors:

DC Current Gain (hFE) (Min) @ Ic, Vce: 20 or greater
Vce Saturation characteristics within acceptable operating margins
RoHS3 Compliance

Substitute parts are grouped into two categories: Direct Equivalents (matching all primary criteria) and Similar Parts (meeting primary electrical requirements with variations in secondary parameters such as power dissipation, frequency response, or current gain characteristics).

Parameter Comparison

Part Number	Manufacturer	Ic (Max)	Vce Breakdown (Max)	Power (Max)	Vce Sat @ Ib, Ic	hFE (Min) @ Ic, Vce	Temp Range	Product Status
BD743A-S	Bourns Inc.	15 A	60 V	2 W	3 V @ 5 A, 15 A	20 @ 5 A, 4 V	-65°C ~ 150°C	Obsolete
2N6487G	onsemi	15 A	60 V	1.8 W	3.5 V @ 5 A, 15 A	20 @ 5 A, 4 V	-65°C ~ 150°C	Active
2N6292G	onsemi	7 A	70 V	40 W	3.5 V @ 3 A, 7 A	30 @ 2 A, 4 V	-65°C ~ 150°C	Active
2ST31A	STMicroelectronics	3 A	60 V	40 W	1.2 V @ 375 mA, 3 A	100 @ 20 mA, 4 V	-65°C ~ 150°C	Active
D44H8	STMicroelectronics	10 A	60 V	50 W	1 V @ 400 mA, 8 A	40 @ 4 A, 1 V	-65°C ~ 150°C	Active
MJE3055T	NTE Electronics, Inc	10 A	60 V	75 W	8 V @ 3.3 A, 10 A	20 @ 4 A, 4 V	-55°C ~ 150°C	Active
MJE3055TG	onsemi	10 A	60 V	75 W	8 V @ 3.3 A, 10 A	20 @ 4 A, 4 V	-55°C ~ 150°C	Active
TIP29A	Solid State Inc.	Not Specified	Not Specified	Not Specified	Not Specified	Not Specified	Not Specified	Active
TIP29AG	onsemi	1 A	60 V	2 W	700 mV @ 125 mA, 1 A	15 @ 1 A, 4 V	-65°C ~ 150°C	Active
TIP31A	Solid State Inc.	3 A	60 V	40 W	1.2 V @ 375 mA, 3 A	25 @ 1 A, 4 V	-65°C ~ 150°C	Active
TIP41AG	onsemi	6 A	60 V	2 W	1.5 V @ 600 mA, 6 A	15 @ 3 A, 4 V	-65°C ~ 150°C	Last Time Buy

Engineering Selection Recommendations

Direct Equivalent:

The 2N6487G from onsemi is the primary direct equivalent to the BD743A-S. This part matches the critical electrical specifications: 15 A maximum collector current, 60 V collector-emitter breakdown voltage, and identical DC current gain characteristics (20 @ 5 A, 4 V). The 2N6487G operates across the same temperature range (-65°C to 150°C) and is housed in the TO-220-3 package. The part is currently in active production status with ROHS3 compliance and REACH unaffected designation, providing long-term supply assurance. The marginal difference in Vce saturation (3.5 V versus 3 V) and power rating (1.8 W versus 2 W) does not preclude functional equivalence in most applications.

Alternative Selections Based on Application Requirements:

For applications requiring higher current capacity within the 60 V rating, the D44H8 from STMicroelectronics provides 10 A maximum collector current with superior power dissipation (50 W) and improved Vce saturation characteristics (1 V @ 400 mA, 8 A). This part is active and ROHS3 compliant.

For applications where higher power dissipation is beneficial, the MJE3055TG from onsemi or MJE3055T from NTE Electronics deliver 75 W maximum power with 10 A collector current at 60 V breakdown voltage. Both parts maintain active production status and ROHS3 compliance.

The TIP41AG from onsemi provides 6 A collector current at 60 V with active production status, though it carries a Last Time Buy designation. This part is suitable for lower-current applications requiring the BD743A-S voltage and package specifications.

Parts Not Recommended:

The TIP29A from Solid State Inc. lacks sufficient electrical parameter documentation for reliable substitution determination. The TIP29AG from onsemi is limited to 1 A maximum collector current, falling below the BD743A-S 15 A specification. The 2ST31A and TIP31A are limited to 3 A maximum collector current, insufficient for full-current applications. The 2N6292G provides only 7 A collector current, below the 15 A requirement.

Frequently Asked Questions (FAQ)

Q: Can the 2N6487G directly replace the BD743A-S in all applications?

A: The 2N6487G matches the critical electrical parameters of the BD743A-S: 15 A maximum collector current, 60 V collector-emitter breakdown voltage, identical DC current gain (20 @ 5 A, 4 V), and TO-220-3 package. The minor differences in Vce saturation (3.5 V versus 3 V) and power rating (1.8 W versus 2 W) are within acceptable engineering margins for most circuit designs. Verification of thermal management and saturation voltage tolerance in the specific application is required.

Q: What is the difference between direct equivalents and similar parts?

A: Direct equivalents match all primary electrical specifications: collector current, breakdown voltage, current gain, and operating temperature range. Similar parts meet the voltage and package requirements but may have different current ratings or power dissipation characteristics. Selection depends on whether the application requires the full 15 A capability or can operate at reduced current levels.

Q: Why do some substitute parts have higher power ratings than the BD743A-S?

A: Higher power ratings indicate improved thermal characteristics and heat dissipation capability in the same TO-220-3 package. Parts such as the D44H8 (50 W) and MJE3055TG (75 W) can handle the same electrical stresses with better thermal performance, making them suitable for applications with elevated ambient temperatures or continuous operation at maximum current.

Q: Is the TIP29AG suitable as a substitute?

A: The TIP29AG is limited to 1 A maximum collector current, which is significantly below the BD743A-S 15 A specification. This part is suitable only for applications requiring substantially lower current levels and cannot serve as a general substitute for the BD743A-S.

Q: What packaging considerations apply to these substitutes?

A: All recommended substitute parts use the TO-220-3 through-hole package, identical to the BD743A-S. This ensures mechanical compatibility with existing printed circuit board layouts and thermal management solutions. No package conversion or board redesign is required.

Q: Are all substitute parts RoHS3 compliant?

A: All recommended substitute parts carry ROHS3 compliance certification, matching the environmental and regulatory status of the BD743A-S. This ensures compatibility with modern manufacturing and supply chain requirements.

Q: What is the significance of "Last Time Buy" status for the TIP41AG?

A: Last Time Buy status indicates that the manufacturer has announced the end of production for this part. While currently available, future availability cannot be assured. For new designs or long-term production requirements, selection of parts with Active production status (such as 2N6487G or D44H8) is recommended.

Q: Can I use a substitute part with lower current rating if my application does not require 15 A?

A: Yes, provided the substitute part's maximum collector current meets or exceeds the actual circuit requirement. For example, the D44H8 (10 A) or 2ST31A (3 A) are suitable for applications requiring less than their rated current. However, the 2N6487G remains the preferred choice when the full 15 A capability is available, as it provides the closest electrical match to the BD743A-S.

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