BA979S-GS18 Equivalent & Substitute Parts

Part Overview

The BA979S-GS18 is an RF Diode PIN - Single rated for 30V peak reverse voltage with 50 mA maximum current, packaged in SOD-80 QuadroMELF. This part is classified as obsolete. Substitute parts are necessary to maintain design continuity and ensure component availability for new production runs and field replacements.

Key Parameters

Parameter	Value
Diode Type	PIN - Single
Voltage - Peak Reverse (Max)	30V
Current - Max	50 mA
Capacitance @ Vr, F	0.5pF @ 0V, 100MHz
Resistance @ If, F	50Ohm @ 1.5mA, 100MHz
Operating Temperature	125°C (TJ)
Package / Case	SOD-80 QuadroMELF
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the BA979S-GS18 is organized into two categories based on allowed electrical and mechanical parameters:

Category 1: Direct Electrical Equivalent (Same Voltage & Current Rating)

BA679S-GS18: Identical electrical specifications (30V, 50 mA) with different packaging (SOD-80 MiniMELF instead of QuadroMELF). This part maintains the same diode type, voltage rating, current rating, capacitance, and resistance characteristics. Product status is active.

Category 2: Higher Voltage & Power Rating Alternatives

MA4P1250-1072T, MA4P7001F-1072T, MA4P7002F-1072T, MA4P7006F-1072T, MA4P7101F-1072T, MA4P7102F-1072T, MA4P7104F-1072T: These MACOM parts exceed the original voltage and power specifications. They are suitable only when circuit design permits higher voltage ratings and can accommodate different package geometries (MELF or ODS-1072). All are active products with extended temperature ranges (-55°C to 175°C).

Substitution eligibility is determined by:

Diode Type: PIN - Single (all candidates match)
Voltage Rating: Must equal or exceed 30V
Current Handling: Must equal or exceed 50 mA
Package Compatibility: Physical footprint and mounting method
Product Status: Active status preferred for new designs
Compliance: ROHS3 and REACH requirements

Parameter Comparison

Part Number	Manufacturer	Voltage (Max)	Current (Max)	Capacitance	Resistance	Power Dissipation	Operating Temp	Package	Product Status
BA979S-GS18	Vishay	30V	50 mA	0.5pF @ 0V, 100MHz	50Ohm @ 1.5mA, 100MHz	—	125°C	SOD-80 QuadroMELF	Obsolete
BA679S-GS18	Vishay	30V	50 mA	0.5pF @ 0V, 100MHz	50Ohm @ 1.5mA, 100MHz	—	125°C	SOD-80 MiniMELF	Active
MA4P1250-1072T	MACOM	100V	—	1.2pF @ 50V, 1MHz	750mOhm @ 50mA, 100MHz	6 W	-55°C ~ 175°C	MELF	Active
MA4P7001F-1072T	MACOM	100V	—	—	900mOhm @ 100mA, 100MHz	10 W	-55°C ~ 175°C	2-SMD	Active
MA4P7002F-1072T	MACOM	200V	—	—	900mOhm @ 100mA, 100MHz	10 W	-55°C ~ 175°C	2-SMD	Active
MA4P7006F-1072T	MACOM	600V	—	—	900mOhm @ 100mA, 100MHz	10 W	-55°C ~ 175°C	2-SMD	Active
MA4P7101F-1072T	MACOM	200V	—	1pF @ 100V, 1MHz	500mOhm @ 100mA, 100MHz	11.5 W	-55°C ~ 175°C	ODS-1072	Active
MA4P7102F-1072T	MACOM	200V	—	—	500mOhm @ 100mA, 100MHz	11.5 W	-55°C ~ 175°C	2-SMD	Active
MA4P7104F-1072T	MACOM	400V	—	—	500mOhm @ 100mA, 100MHz	11.5 W	-55°C ~ 175°C	2-SMD	Active

Engineering Selection Recommendations

For Direct Replacement (Preferred for Existing Designs): BA679S-GS18 is the primary substitute. It maintains identical electrical specifications and compliance certifications (ROHS3, REACH Unaffected). The only difference is packaging format (MiniMELF vs. QuadroMELF). This part is active and has 754 units in stock. PCB layout modification is required to accommodate the different package footprint.

For New Designs or Higher Performance Requirements: MACOM MA4P series parts are suitable when circuit design permits higher voltage ratings and increased power dissipation. These parts offer extended operating temperature ranges (-55°C to 175°C vs. 125°C) and active product status. Selection within the MA4P series depends on specific voltage and power requirements:

MA4P1250-1072T: 100V, 6W (lowest power option)
MA4P7001F-1072T: 100V, 10W
MA4P7002F-1072T: 200V, 10W
MA4P7006F-1072T: 600V, 10W
MA4P7101F-1072T: 200V, 11.5W (lowest resistance at 100mA)
MA4P7102F-1072T: 200V, 11.5W
MA4P7104F-1072T: 400V, 11.5W

All MACOM alternatives are ROHS3 compliant and carry active product status with substantial inventory availability.

Frequently Asked Questions (FAQ)

Q: Can BA679S-GS18 be used as a direct drop-in replacement for BA979S-GS18? A: Electrically yes, but mechanically no. Both parts have identical voltage (30V), current (50 mA), capacitance, and resistance specifications. However, BA679S-GS18 uses SOD-80 MiniMELF packaging while BA979S-GS18 uses SOD-80 QuadroMELF. PCB layout and footprint modifications are required.

Q: Why are MACOM parts listed as substitutes if they have higher voltage ratings? A: Higher voltage ratings do not prevent substitution; they expand application capability. A 100V or 200V rated diode functions correctly in a 30V circuit. Selection of MACOM parts is appropriate when circuit design permits higher voltage margins or when higher power dissipation is beneficial.

Q: What is the difference between SOD-80 QuadroMELF and SOD-80 MiniMELF? A: Both are SOD-80 package variants with different physical dimensions. QuadroMELF is larger; MiniMELF is smaller. Electrical performance is identical for BA979S-GS18 and BA679S-GS18. Package selection depends on available PCB space and design constraints.

Q: Are all substitute parts ROHS3 compliant? A: Yes. BA679S-GS18 and all MACOM MA4P series parts are ROHS3 compliant. All are REACH Unaffected.

Q: Which substitute has the lowest resistance at operating current? A: MA4P7101F-1072T and MA4P7102F-1072T both offer 500mOhm @ 100mA, 100MHz, compared to 50Ohm @ 1.5mA for the original BA979S-GS18. Direct resistance comparison is not applicable due to different measurement conditions.

Q: What is the inventory status of substitute parts? A: BA679S-GS18 has 754 units in stock. MACOM parts have substantial inventory: MA4P1250-1072T (305,200 units), MA4P7001F-1072T (21,200 units), MA4P7002F-1072T (5,930 units), MA4P7006F-1072T (1,533 units), MA4P7101F-1072T (19,180 units), MA4P7102F-1072T (17,300 units), MA4P7104F-1072T (4,800 units).

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