LS4148WS Equivalent & Substitute Parts

Part Overview

The LS4148WS is a general-purpose surface mount diode manufactured by Diodes Incorporated, rated for 75 V DC reverse voltage and 150 mA average rectified current. This component is classified as a small signal diode with a reverse recovery time of 4 ns, housed in a 0805 (2012 Metric) package. The LS4148WS is currently listed as obsolete, which necessitates identification of functionally equivalent active alternatives for new designs and ongoing production requirements.

Key Parameters

Parameter	Value
Voltage - DC Reverse (Vr) (Max)	75 V
Current - Average Rectified (Io)	150 mA
Voltage - Forward (Vf) (Max) @ If	1 V @ 10 mA
Reverse Recovery Time (trr)	4 ns
Current - Reverse Leakage @ Vr	5 µA @ 75 V
Capacitance @ Vr, F	4 pF @ 0 V, 1 MHz
Mounting Type	Surface Mount
Package / Case	0805 (2012 Metric)
Operating Temperature - Junction	-65°C ~ 175°C
Technology	Standard
Speed Classification	Small Signal ≤ 200 mA (Io), Any Speed

Substitute Part Grouping Explanation

Substitution of the LS4148WS is determined by electrical and mechanical compatibility across the following critical parameters:

Electrical Compatibility Criteria:

Voltage - DC Reverse (Vr) (Max): Must equal or exceed 75 V
Current - Average Rectified (Io): Must equal or exceed 150 mA
Reverse Recovery Time (trr): Must equal or be faster than 4 ns
Speed Classification: Must maintain Small Signal classification (≤ 200 mA)
Technology: Must be Standard technology

Mechanical Compatibility Criteria:

Mounting Type: Surface Mount required
Operating Temperature Range: Must encompass or match the specified junction temperature range

The substitute part 1N4148WS-7-F meets all electrical requirements and maintains surface mount compatibility. However, the package format differs from the original 0805 specification, requiring board-level design verification for physical fit and thermal management.

Parameter Comparison

Parameter	LS4148WS	1N4148WS-7-F	Match Status
Voltage - DC Reverse (Vr) (Max)	75 V	75 V	Equal
Current - Average Rectified (Io)	150 mA	150 mA	Equal
Voltage - Forward (Vf) (Max) @ If	1 V @ 10 mA	1.25 V @ 150 mA	Different Test Conditions
Reverse Recovery Time (trr)	4 ns	4 ns	Equal
Current - Reverse Leakage @ Vr	5 µA @ 75 V	1 µA @ 75 V	1N4148WS-7-F Superior
Capacitance @ Vr, F	4 pF @ 0 V, 1 MHz	2 pF @ 0 V, 1 MHz	1N4148WS-7-F Superior
Mounting Type	Surface Mount	Surface Mount	Equal
Package / Case	0805 (2012 Metric)	SC-76, SOD-323	Different
Operating Temperature - Junction	-65°C ~ 175°C	-65°C ~ 150°C	1N4148WS-7-F Narrower Range
Technology	Standard	Standard	Equal
Speed Classification	Small Signal ≤ 200 mA	Small Signal ≤ 200 mA	Equal
Product Status	Obsolete	Active	Substitute is Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Equal

Engineering Selection Recommendations

The 1N4148WS-7-F is the manufacturer-recommended substitute for the obsolete LS4148WS. Both components are manufactured by Diodes Incorporated and maintain ROHS3 compliance and REACH unaffected status.

Selection Basis:

The 1N4148WS-7-F satisfies all critical electrical parameters: reverse voltage rating (75 V), average rectified current (150 mA), reverse recovery time (4 ns), and small signal speed classification. The substitute demonstrates improved performance characteristics in reverse leakage current (1 µA versus 5 µA) and junction capacitance (2 pF versus 4 pF).

Design Considerations:

The primary design change involves package format transition from 0805 (2012 Metric) to SOD-323 (SC-76). This package change requires PCB layout modification and must be evaluated for space constraints and thermal performance in the target application. The operating temperature range of the substitute extends to 150°C maximum junction temperature, compared to 175°C for the original part. Applications requiring operation above 150°C require alternative component selection.

Frequently Asked Questions (FAQ)

Q: Can the 1N4148WS-7-F directly replace the LS4148WS without PCB modification?

A: No. The package formats differ fundamentally. The LS4148WS uses 0805 (2012 Metric) surface mount package, while the 1N4148WS-7-F uses SOD-323 (SC-76) package. PCB footprint redesign is required.

Q: Are the electrical specifications compatible for circuit operation?

A: Yes. Both components share identical voltage ratings (75 V), current ratings (150 mA), and reverse recovery time (4 ns). The 1N4148WS-7-F exhibits superior reverse leakage current and lower junction capacitance, which may improve circuit performance.

Q: What is the significance of the different forward voltage specifications?

A: The forward voltage measurements are conducted at different test conditions. The LS4148WS specifies 1 V at 10 mA, while the 1N4148WS-7-F specifies 1.25 V at 150 mA. Both values are within acceptable ranges for general-purpose diode applications and do not prevent substitution.

Q: Does the operating temperature range difference affect substitution suitability?

A: The 1N4148WS-7-F maximum junction temperature is 150°C, compared to 175°C for the LS4148WS. Applications operating above 150°C require verification that the substitute meets thermal requirements. Most general-purpose applications operate within this range.

Q: Are compliance certifications maintained with the substitute part?

A: Yes. Both the LS4148WS and 1N4148WS-7-F are ROHS3 compliant and REACH unaffected. Regulatory compliance is maintained with substitution.

Q: What is the inventory status of the substitute part?

A: The 1N4148WS-7-F is listed as active product with 1,000,300 pieces in stock, ensuring long-term availability for production requirements.

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