BSS138_L99Z N-Channel MOSFET Equivalent & Substitute Parts

Part Overview

The BSS138_L99Z is an N-Channel MOSFET manufactured by onsemi, rated for 50V drain-to-source voltage with 220mA continuous drain current in a surface mount SOT-23-3 package. This device is classified as obsolete product status. Due to its obsolete classification, equivalent and substitute parts from active product lines are necessary to maintain design continuity and ensure long-term component availability for new production and field replacements.

Key Parameters

Parameter	Value	Unit
FET Type	N-Channel	—
Drain to Source Voltage (Vdss)	50	V
Continuous Drain Current (Id) @ 25°C	220	mA
Rds On (Max) @ Id, Vgs	3.5 @ 220mA, 10V	Ohm
Vgs(th) (Max) @ Id	1.5 @ 1mA	V
Gate Charge (Qg) (Max) @ Vgs	2.4 @ 10V	nC
Vgs (Max)	±20	V
Input Capacitance (Ciss) (Max) @ Vds	27 @ 25V	pF
Power Dissipation (Max)	360	mW
Operating Temperature Range	-55 to 150	°C
Package Type	SOT-23-3	—
Mounting Type	Surface Mount	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the BSS138_L99Z is determined by the following critical parameters:

Electrical Compatibility Requirements:

Drain to Source Voltage (Vdss): Must equal or exceed 50V
Rds On (Max): Must not exceed 3.5 Ohm at specified gate voltage and drain current
Vgs(th) (Max): Must not exceed 1.5V @ 1mA
Vgs (Max): Must support ±20V gate voltage range
Operating Temperature Range: Must encompass -55°C to 150°C minimum

Mechanical Compatibility Requirements:

Package Type: SOT-23-3 (TO-236-3, SC-59)
Mounting Type: Surface Mount
Moisture Sensitivity Level: MSL 1 (Unlimited)

Substitution Categories:

Direct Substitutes (Identical Electrical and Mechanical Specifications): Parts that maintain the same Vdss, Rds On, Vgs(th), and package configuration as the BSS138_L99Z.

Similar Substitutes (Reduced Current Rating): Parts with identical Vdss, Rds On, and Vgs(th) but reduced continuous drain current (200mA vs. 220mA). These are suitable for applications where the full 220mA rating is not required.

Parametric Equivalents (Alternative Manufacturers): Parts from different manufacturers meeting the same electrical specifications and package requirements, providing cross-manufacturer compatibility.

Parameter Comparison

Part Number	Manufacturer	Product Status	Vdss (V)	Id @ 25°C (mA)	Rds On (Ohm)	Vgs(th) (V)	Qg @ 10V (nC)	Ciss @ 25V (pF)	Power Diss. (mW)	Temp Range (°C)	Package
BSS138_L99Z	onsemi	Obsolete	50	220	3.5 @ 10V	1.5 @ 1mA	2.4	27	360	-55 to 150	SOT-23-3
BSS138L	onsemi	Active	50	200	3.5 @ 5V	1.5 @ 1mA	2.4	50	350	-55 to 150	SOT-23-3
BSS138LT1G	onsemi	Active	50	200	3.5 @ 5V	1.5 @ 1mA	—	50	225	-55 to 150	SOT-23-3
BSS138LT3G	onsemi	Active	50	200	3.5 @ 5V	1.5 @ 1mA	—	50	225	-55 to 150	SOT-23-3
BSS138	Good-Ark Semiconductor	Active	50	220	3.5 @ 10V	1.5 @ 250µA	2.4	30	430	-55 to 175	SOT-23
BSS138-G	onsemi	Active	50	220	3.5 @ 10V	1.5 @ 1mA	2.4	27	360	-55 to 150	SOT-23-3
BSS138-7-F	Diodes Incorporated	Active	50	200	3.5 @ 10V	1.5 @ 250µA	—	50	300	-55 to 150	SOT-23-3
BSS138-TP	Micro Commercial Co	Active	50	220	3.5 @ 10V	1.5 @ 1mA	—	60	350	-55 to 150	SOT-23-3

Engineering Selection Recommendations

Primary Recommendation: BSS138-G (onsemi)

The BSS138-G is the direct equivalent substitute for the BSS138_L99Z. Both parts are manufactured by onsemi and share identical electrical specifications: 50V Vdss, 220mA continuous drain current, 3.5 Ohm Rds On at 10V, and 360mW power dissipation. The BSS138-G maintains active product status with RoHS3 compliance and REACH unaffected certification. This part provides pin-for-pin compatibility with no design modifications required.

Secondary Recommendation: BSS138LT1G or BSS138LT3G (onsemi)

These parts are suitable for applications where the continuous drain current requirement is 200mA or less. Both maintain the 50V Vdss rating and 3.5 Ohm Rds On specification. The BSS138LT1G and BSS138LT3G offer reduced power dissipation (225mW vs. 360mW) and are available in high inventory quantities. Both are active products with RoHS3 compliance and REACH unaffected status. These parts are direct pin-compatible replacements in SOT-23-3 packaging.

Alternative Recommendation: BSS138-7-F (Diodes Incorporated)

The BSS138-7-F provides cross-manufacturer compatibility with 50V Vdss and 3.5 Ohm Rds On specification. This part is rated for 200mA continuous drain current and is suitable for applications not requiring the full 220mA rating. The BSS138-7-F is active product with RoHS3 compliance and maintains SOT-23-3 package compatibility.

Cross-Manufacturer Option: BSS138 (Good-Ark Semiconductor)

The Good-Ark Semiconductor BSS138 matches the 220mA current rating and 3.5 Ohm Rds On of the original part. This parametric equivalent extends the operating temperature range to 175°C and is available in high inventory. RoHS3 compliance and REACH unaffected status are confirmed. Package designation is SOT-23 (compatible with SOT-23-3 footprint).

Packaging Consideration: BSS138-TP (Micro Commercial Co)

The BSS138-TP is supplied in Tape & Reel (TR) packaging and matches the 220mA current rating and electrical specifications of the BSS138_L99Z. This part is active product with RoHS3 compliance and is suitable for high-volume production environments requiring reel packaging.

Frequently Asked Questions (FAQ)

Q: Can BSS138L or BSS138LT1G be used as direct replacements for BSS138_L99Z?

A: BSS138L and BSS138LT1G are pin-compatible substitutes in SOT-23-3 packaging. Both maintain the 50V Vdss and 3.5 Ohm Rds On specifications. The primary difference is reduced continuous drain current (200mA vs. 220mA). These parts are suitable for applications where the full 220mA rating is not required. Both are active products from onsemi with RoHS3 compliance.

Q: What is the difference between BSS138-G and BSS138_L99Z?

A: BSS138-G is the active product equivalent of the obsolete BSS138_L99Z. Both parts share identical electrical specifications: 50V Vdss, 220mA continuous drain current, 3.5 Ohm Rds On at 10V, 2.4 nC gate charge, and 360mW power dissipation. The BSS138-G is manufactured by onsemi and maintains the same SOT-23-3 package. No design modifications are required for substitution.

Q: Are there differences in gate charge or input capacitance between substitute parts?

A: Yes. The BSS138_L99Z specifies 27 pF input capacitance at 25V. Substitute parts show variation: BSS138L and BSS138LT1G specify 50 pF, BSS138-7-F specifies 50 pF, and BSS138-TP specifies 60 pF. The Good-Ark BSS138 specifies 30 pF. These differences may affect switching speed in high-frequency applications. Gate charge specifications are consistent at 2.4 nC across most parts.

Q: Can I use BSS138-7-F from Diodes Incorporated as a substitute?

A: Yes. BSS138-7-F is a direct substitute with 50V Vdss, 3.5 Ohm Rds On, and SOT-23-3 package compatibility. The part is rated for 200mA continuous drain current, which is 20mA lower than the original 220mA rating. BSS138-7-F is active product with RoHS3 compliance and REACH unaffected status. Substitution is suitable for applications not requiring the full 220mA rating.

Q: What is the difference between onsemi BSS138L and BSS138LT1G?

A: Both parts are onsemi products with identical electrical specifications: 50V Vdss, 200mA continuous drain current, 3.5 Ohm Rds On at 5V, and 1.5V Vgs(th). The primary difference is power dissipation: BSS138L specifies 350mW while BSS138LT1G specifies 225mW. Both are active products in SOT-23-3 packaging with RoHS3 compliance. The BSS138LT1G offers improved thermal performance.

Q: Is the Good-Ark Semiconductor BSS138 compatible with the original BSS138_L99Z?

A: Yes. The Good-Ark BSS138 is a parametric equivalent with matching 50V Vdss, 220mA continuous drain current, and 3.5 Ohm Rds On specifications. The part is supplied in SOT-23 packaging, which is footprint-compatible with SOT-23-3. The Good-Ark part extends the operating temperature range to 175°C and is active product with RoHS3 compliance and high inventory availability.

Q: What packaging options are available for BSS138 substitutes?

A: Most substitute parts are available in Cut Tape (CT) & Digi-Reel® packaging. BSS138-TP from Micro Commercial Co is supplied in Tape & Reel (TR) format, suitable for automated assembly and high-volume production. All parts maintain SOT-23-3 or compatible SOT-23 package footprints for direct PCB compatibility.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All active substitute parts listed (BSS138L, BSS138LT1G, BSS138LT3G, BSS138-G, BSS138-7-F, BSS138-TP, and Good-Ark BSS138) are confirmed RoHS3 compliant. All parts maintain REACH unaffected status and MSL 1 (Unlimited) moisture sensitivity rating.

Q: Which substitute offers the lowest power dissipation?

A: BSS138LT1G and BSS138LT3G both specify 225mW power dissipation, which is the lowest among active substitutes. These parts are suitable for applications where thermal management is a design constraint. Both maintain 50V Vdss and 3.5 Ohm Rds On specifications with 200mA continuous drain current rating.

Q: Can I substitute BSS138-TP for BSS138_L99Z in new production?

A: Yes. BSS138-TP from Micro Commercial Co matches the 220mA current rating and electrical specifications of the original part. The primary difference is packaging format: BSS138-TP is supplied in Tape & Reel (TR) format rather than Cut Tape. This part is active product with RoHS3 compliance and is suitable for high-volume production environments.

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