2N6038 Equivalent & Substitute Parts

Part Overview

The 2N6038 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 through-hole package. This device is classified as obsolete, making equivalent substitute parts necessary for new designs and production continuity. The 2N6038 delivers 40 W maximum power dissipation with a minimum DC current gain of 750 at specified operating conditions, suitable for switching and amplification applications requiring moderate voltage and current ratings.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN - Darlington	—
Current - Collector (Ic) (Max)	4	A
Voltage - Collector Emitter Breakdown (Max)	60	V
Power - Max	40	W
DC Current Gain (hFE) (Min)	750	—
Mounting Type	Through Hole	—
Package / Case	TO-225AA, TO-126-3	—
Operating Temperature Range	-65 to 150	°C

Substitute Part Grouping Explanation

Substitute parts for the 2N6038 are selected based on electrical parameter compatibility within the allowed specifications for NPN Darlington transistors. The primary substitution criteria are:

Electrical Parameters:

Maximum collector current (Ic) of 4 A or greater
Maximum collector-emitter breakdown voltage (Vce) of 60 V or greater
Maximum power dissipation of 40 W or greater
DC current gain (hFE) minimum of 750 or greater
NPN Darlington transistor configuration

Mechanical Parameters:

Through-hole mounting type
TO-225AA or TO-126-3 package compatibility

Compliance Parameters:

RoHS compliance status
REACH compliance status

The substitute parts BD677, BD677A, and BD681 meet or exceed these electrical and mechanical requirements. BD677 and BD677A are direct voltage-rated equivalents at 60 V, while BD681 provides enhanced voltage rating at 100 V, allowing operation in higher-voltage applications while maintaining backward compatibility with 60 V designs.

Parameter Comparison

Parameter	2N6038 (onsemi)	BD677 (STMicroelectronics)	BD677A (STMicroelectronics)	BD681 (STMicroelectronics)
Transistor Type	NPN - Darlington	NPN - Darlington	NPN - Darlington	NPN - Darlington
Current - Collector (Ic) (Max)	4 A	4 A	4 A	4 A
Voltage - Collector Emitter Breakdown (Max)	60 V	60 V	60 V	100 V
Power - Max	40 W	40 W	40 W	40 W
DC Current Gain (hFE) (Min) @ Ic, Vce	750 @ 2A, 3V	750 @ 1.5A, 3V	750 @ 2A, 3V	750 @ 1.5A, 3V
Current - Collector Cutoff (Max)	100 µA	500 µA	500 µA	500 µA
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	TO-225AA, TO-126-3	TO-225AA, TO-126-3	TO-225AA, TO-126-3	TO-225AA, TO-126-3
Supplier Device Package	TO-126	SOT-32-3	SOT-32-3	SOT-32-3
Operating Temperature (TJ)	-65 to 150 °C	150 °C	150 °C	150 °C
Product Status	Obsolete	Active	Active	Active
RoHS Status	Non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

BD677 and BD677A Selection: BD677 and BD677A are direct electrical equivalents to the 2N6038, maintaining the 60 V collector-emitter breakdown voltage rating. Both parts are manufactured by STMicroelectronics and carry active product status with ROHS3 compliance, providing long-term availability and regulatory alignment. BD677A matches the 2N6038 DC current gain specification at 2 A collector current, making it the preferred direct replacement for applications requiring identical electrical characteristics. BD677 operates at lower collector current conditions (1.5 A) for gain specification but remains functionally compatible.

BD681 Selection: BD681 provides a higher voltage rating of 100 V while maintaining all other electrical parameters at or above 2N6038 specifications. This part is suitable for applications requiring enhanced voltage margin or operation in higher-voltage environments. The 100 V rating does not degrade performance in 60 V applications and offers design flexibility for future voltage requirement changes.

Compliance Considerations: All three substitute parts are ROHS3 compliant and REACH unaffected, meeting modern regulatory requirements. The 2N6038 is RoHS non-compliant, making substitution necessary for applications subject to RoHS directives.

Availability: BD677A offers the highest inventory level (2443 pcs), followed by BD681 (10400 pcs) and BD677 (1804 pcs), ensuring supply chain continuity for production requirements.

Frequently Asked Questions (FAQ)

Q: Can BD677 directly replace the 2N6038 in existing designs? A: BD677 is electrically compatible with the 2N6038, meeting the 60 V voltage rating and 4 A current rating. Both parts are NPN Darlington transistors in through-hole packages. Physical package dimensions should be verified for PCB layout compatibility, as the 2N6038 uses TO-126 packaging while BD677 uses SOT-32-3 packaging.

Q: What is the difference between BD677 and BD677A? A: BD677 and BD677A are both 60 V rated NPN Darlington transistors with identical maximum ratings. The primary difference is the DC current gain specification point: BD677A specifies 750 hFE minimum at 2 A collector current (matching the 2N6038), while BD677 specifies this gain at 1.5 A. For applications requiring the exact gain specification of the 2N6038, BD677A is the preferred choice.

Q: Why would BD681 be selected over BD677 or BD677A? A: BD681 provides a 100 V collector-emitter breakdown voltage rating compared to 60 V for BD677 and BD677A. Selection of BD681 is appropriate for applications operating at higher voltages or requiring additional voltage safety margin. The 100 V rating is backward compatible with 60 V designs and does not introduce performance degradation.

Q: Are there package compatibility concerns when substituting these parts? A: The 2N6038 is supplied in TO-126 packaging, while BD677, BD677A, and BD681 are supplied in SOT-32-3 packaging. Both package types are through-hole configurations with TO-225AA and TO-126-3 case designations. Physical lead spacing and PCB hole patterns must be verified before substitution to ensure mechanical fit.

Q: What is the significance of the collector cutoff current difference? A: The 2N6038 specifies a maximum collector cutoff current of 100 µA, while all three substitute parts specify 500 µA. This parameter represents leakage current when the transistor is in the off state. The higher cutoff current in substitute parts may result in slightly increased leakage in off-state conditions but does not affect switching or amplification performance in typical applications.

Q: Are all substitute parts RoHS compliant? A: Yes. BD677, BD677A, and BD681 are all ROHS3 compliant. The 2N6038 is RoHS non-compliant. For applications subject to RoHS directives or customer requirements, substitution with any of these three parts ensures regulatory compliance.

Q: Can these parts be used interchangeably in the same circuit? A: BD677, BD677A, and BD681 can be used interchangeably in circuits designed for the 2N6038 from an electrical standpoint, provided the circuit operates at or below 60 V (for BD677 and BD677A) or 100 V (for BD681). Physical package differences require PCB layout verification. The higher collector cutoff current in substitute parts should be evaluated in applications where leakage current is critical.

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