BSS138TC N-Channel MOSFET Equivalent & Substitute Parts

Part Overview

The BSS138TC is an N-Channel MOSFET manufactured by Diodes Incorporated, rated for 50V drain-to-source voltage with 200mA continuous drain current in a surface mount SOT-23-3 package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

The BSS138TC serves in low-power switching applications requiring compact form factors and moderate voltage ratings. Substitute parts maintain electrical and mechanical compatibility while offering active product status and improved availability.

Key Parameters

Parameter	Value	Unit
FET Type	N-Channel	—
Technology	MOSFET (Metal Oxide)	—
Drain to Source Voltage (Vdss)	50	V
Continuous Drain Current (Id) @ 25°C	200	mA
Rds On (Max) @ 220mA, 10V	3.5	Ohm
Gate Threshold Voltage (Vgs(th)) (Max)	1.5	V @ 250µA
Gate Voltage (Vgs) (Max)	±20	V
Input Capacitance (Ciss) (Max) @ 10V	50	pF
Power Dissipation (Max)	300	mW
Operating Temperature Range	-55 to 150	°C
Package Type	SOT-23-3	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the BSS138TC is determined by strict equivalence across the following critical parameters:

Electrical Equivalence Criteria:

Drain-to-Source Voltage (Vdss): 50V minimum
Continuous Drain Current (Id): 200mA minimum at 25°C
Gate Threshold Voltage (Vgs(th)): 1.5V maximum
Gate Voltage (Vgs): ±20V maximum rating
On-State Resistance (Rds On): 3.5 Ohm maximum at specified conditions
Package compatibility: SOT-23-3 (TO-236-3, SC-59)

Mechanical Equivalence Criteria:

Surface mount technology
SOT-23-3 package footprint
Identical pin configuration

Compliance Equivalence Criteria:

RoHS3 compliance
MSL Level 1 (Unlimited moisture sensitivity)
REACH unaffected status

Substitute parts listed below meet all electrical parameters at or above the BSS138TC specification, maintain identical mechanical packaging, and carry active product status with established supply chains.

Parameter Comparison

Parameter	BSS138TC (Diodes)	BSS138-7-F (Diodes)	BSS138 (Good-Ark)	BSS138-TP (MCC)	BSS138L (onsemi)	BSS138LT1G (onsemi)	BSS138LT3G (onsemi)
Manufacturer	Diodes Inc.	Diodes Inc.	Good-Ark Semi.	Micro Commercial	onsemi	onsemi	onsemi
Product Status	Obsolete	Active	Active	Active	Active	Active	Active
Vdss (V)	50	50	50	50	50	50	50
Id @ 25°C (mA)	200	200	220	220	200	200	200
Rds On (Max) @ 10V (Ohm)	3.5	3.5	3.5	3.5	3.5	3.5	3.5
Vgs(th) (Max) (V)	1.5	1.5	1.5	1.5	1.5	1.5	1.5
Vgs (Max) (V)	±20	±20	±20	±20	±20	±20	±20
Ciss (Max) @ 10V (pF)	50	50	30	60	50	50	50
Power Dissipation (Max) (mW)	300	300	430	350	350	225	225
Operating Temperature (°C)	-55 to 150	-55 to 150	-55 to 175	-55 to 150	-55 to 150	-55 to 150	-55 to 150
Package	SOT-23-3	SOT-23-3	SOT-23	SOT-23	SOT-23-3	SOT-23-3	SOT-23-3
RoHS Status	ROHS3	ROHS3	ROHS3	ROHS3	ROHS3	ROHS3	ROHS3
MSL	1	1	1	1	1	1	1

Engineering Selection Recommendations

Primary Substitute: BSS138-7-F (Diodes Incorporated)

The BSS138-7-F is the direct equivalent from the same manufacturer as the obsolete BSS138TC. It maintains identical electrical specifications, package configuration, and compliance certifications. This part carries active product status with substantial inventory availability (905,100 pcs), ensuring long-term supply continuity. Selection of this part eliminates any cross-manufacturer compatibility concerns.

Secondary Substitutes: BSS138L and BSS138LT1G/LT3G (onsemi)

The onsemi BSS138L, BSS138LT1G, and BSS138LT3G variants meet all critical electrical parameters and maintain SOT-23-3 packaging. These parts carry active status with established supply chains. The BSS138LT1G and BSS138LT3G offer reduced power dissipation (225mW vs. 300mW), providing thermal margin in power-constrained applications. All three onsemi variants are ROHS3 compliant with MSL Level 1 rating.

Alternative Substitutes: BSS138 (Good-Ark Semiconductor) and BSS138-TP (Micro Commercial Co)

The Good-Ark BSS138 and Micro Commercial BSS138-TP meet electrical specifications with enhanced drain current ratings (220mA vs. 200mA). Both parts maintain SOT-23 package compatibility and active product status. The Good-Ark variant supports extended operating temperature to 175°C. These alternatives provide additional sourcing flexibility when primary substitutes face supply constraints.

Compliance Verification:

All substitute parts listed carry ROHS3 compliance, MSL Level 1 rating, and REACH unaffected status, matching the BSS138TC environmental and regulatory requirements. No additional qualification is required for applications previously using the BSS138TC.

Frequently Asked Questions (FAQ)

Q: Can BSS138-7-F directly replace BSS138TC without circuit modification?

A: Yes. The BSS138-7-F is electrically and mechanically equivalent to the BSS138TC. Identical Vdss (50V), Id (200mA), Rds On (3.5Ω), and SOT-23-3 packaging enable direct substitution without design changes.

Q: What is the difference between BSS138L and BSS138LT1G?

A: Both parts are onsemi N-Channel MOSFETs with identical electrical ratings (50V, 200mA, 3.5Ω Rds On). The primary difference is power dissipation: BSS138L rated at 350mW versus BSS138LT1G at 225mW. The BSS138LT1G provides superior thermal performance in thermally constrained designs.

Q: Are onsemi BSS138 variants compatible with the original BSS138TC footprint?

A: Yes. All onsemi variants (BSS138L, BSS138LT1G, BSS138LT3G) use SOT-23-3 packaging with identical pin configuration to the BSS138TC. PCB footprints are directly compatible.

Q: Why does Good-Ark BSS138 specify 220mA drain current instead of 200mA?

A: The Good-Ark BSS138 is rated for 220mA continuous drain current, exceeding the BSS138TC specification of 200mA. This higher rating provides additional current margin while maintaining the same 3.5Ω on-state resistance. The part remains fully compatible for applications designed around the 200mA specification.

Q: Can I use BSS138-TP (Micro Commercial) in place of BSS138TC?

A: Yes. The BSS138-TP meets all critical electrical parameters: 50V Vdss, 220mA Id, 3.5Ω Rds On, and SOT-23 packaging. It is electrically and mechanically compatible with the BSS138TC.

Q: What is the significance of the "LT" designation in BSS138LT1G and BSS138LT3G?

A: The "LT" designation indicates onsemi's low-temperature coefficient variant. These parts maintain consistent performance across the full operating temperature range (-55°C to 150°C) with reduced thermal drift compared to standard BSS138L. The "1G" and "3G" suffixes denote different tape reel configurations for automated assembly.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All substitute parts listed (BSS138-7-F, BSS138, BSS138-TP, BSS138L, BSS138LT1G, BSS138LT3G) carry ROHS3 compliance certification, matching the BSS138TC environmental standard.

Q: Which substitute offers the best thermal performance?

A: The BSS138LT1G and BSS138LT3G offer the lowest power dissipation rating at 225mW, compared to 300mW for the BSS138TC. These parts are optimal for applications requiring maximum thermal margin.

Q: Is inventory availability a factor in selecting a substitute?

A: Yes. The BSS138-7-F (905,100 pcs) and BSS138LT1G (905,200 pcs) offer the highest inventory levels, ensuring long-term supply security. The BSS138-TP (4,200 pcs) has more limited availability and should be evaluated based on project timeline requirements.

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