OPA124U Equivalent & Substitute Parts Reference

Part Overview

The OPA124U is a general-purpose operational amplifier manufactured by Texas Instruments in the Difet® series, housed in an 8-SOIC surface-mount package. This device is classified as obsolete, making equivalent and substitute parts necessary for new designs and production continuity. The OPA124U delivers 1 circuit with a 1.5 MHz gain-bandwidth product and operates across a 10V to 36V supply range, suitable for general-purpose amplification applications requiring low input bias current (1 pA) and moderate slew rate performance.

Key Parameters

Parameter	OPA124U Value	Unit
Amplifier Type	General Purpose	—
Number of Circuits	1	—
Slew Rate	1.6	V/µs
Gain Bandwidth Product	1.5	MHz
Current - Input Bias	1	pA
Voltage - Input Offset	200	µV
Current - Supply	2.5	mA
Current - Output / Channel	10	mA
Voltage - Supply Span (Min)	10	V
Voltage - Supply Span (Max)	36	V
Operating Temperature Range	-25 to 85	°C
Package / Case	8-SOIC (0.154", 3.90mm Width)	—
Mounting Type	Surface Mount	—
Product Status	Obsolete	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the OPA124U is determined by strict alignment of electrical and mechanical parameters within the operational amplifier category. The following criteria establish valid substitute relationships:

Primary Substitution Criteria:

Package compatibility: 8-SOIC surface-mount form factor (0.154", 3.90mm width)
Supply voltage range: Minimum 10V to maximum 36V overlap
Number of circuits: Single circuit configuration
Mounting type: Surface mount

Secondary Electrical Compatibility Factors:

Slew rate: Substitute must meet or exceed 1.6 V/µs
Gain bandwidth product: Substitute must meet or exceed 1.5 MHz
Input bias current: Substitute must not exceed 1 pA significantly
Input offset voltage: Substitute must not exceed 200 µV significantly
Output current capability: Substitute must provide minimum 10 mA per channel
Supply current: Substitute must not exceed 2.5 mA significantly

Compliance Requirements:

RoHS3 compliance mandatory
REACH unaffected status required
EAR99 classification maintained

The substitute parts listed below satisfy these criteria through either direct electrical equivalence or functional superiority within specified parameter boundaries.

Parameter Comparison

Parameter	OPA124U	OPA145ID	AD825ARZ	AD825ARZ-REEL	AD825ARZ-REEL7	LT1008S8#PBF	LT1008S8#TRPBF	Unit
Amplifier Type	General Purpose	J-FET	J-FET	J-FET	J-FET	General Purpose	General Purpose	—
Number of Circuits	1	1	1	1	1	1	1	—
Slew Rate	1.6	20	140	140	140	0.2	0.2	V/µs
Gain Bandwidth Product	1.5	5.5	26	26	26	—	—	MHz
Current - Input Bias	1	2	15	15	15	100	100	pA
Voltage - Input Offset	200	40	1000	1000	1000	30	30	µV
Current - Supply	2.5	0.445	6.5	6.5	6.5	0.38	0.38	mA
Current - Output / Channel	10	20	50	50	50	—	—	mA
Voltage - Supply Span (Min)	10	4.5	10	10	10	4	4	V
Voltage - Supply Span (Max)	36	36	36	36	36	36	36	V
Operating Temperature Range	-25 to 85	-40 to 125	-40 to 85	-40 to 85	-40 to 85	0 to 70	0 to 70	°C
Package / Case	8-SOIC	8-SOIC	8-SOIC	8-SOIC	8-SOIC	8-SOIC	8-SOIC	—
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	—
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	—

Engineering Selection Recommendations

Active Product Status Advantage: All substitute parts listed carry active product status, ensuring long-term availability and manufacturing support. The OPA124U obsolete status necessitates migration to active alternatives for new designs and ongoing production requirements.

Compliance and Certification Alignment: All substitute parts maintain ROHS3 compliance and REACH unaffected status, matching the OPA124U regulatory framework. EAR99 classification is consistent across all options, supporting identical export and supply chain requirements.

Packaging and Mounting Compatibility: All substitute parts utilize the 8-SOIC surface-mount package with identical 0.154" (3.90mm) width specification, enabling direct PCB layout compatibility without redesign.

Supply Voltage Range Considerations: The OPA124U operates within 10V to 36V. The OPA145ID, AD825ARZ variants, and LT1008S8 options all support the maximum 36V specification. The OPA145ID and LT1008S8 variants extend minimum supply voltage to 4.5V and 4V respectively, providing broader flexibility for lower-voltage applications.

Performance Trade-offs:

OPA145ID: Offers improved slew rate (20 V/µs) and bandwidth (5.5 MHz) with reduced supply current (445 µA), suitable for applications requiring enhanced dynamic performance with lower power consumption.
AD825ARZ variants: Deliver superior slew rate (140 V/µs) and bandwidth (26 MHz) with higher output current (50 mA), appropriate for high-speed signal conditioning and driving capacitive loads.
LT1008S8 variants: Provide lower supply current (380 µA) and improved input offset voltage (30 µV), optimized for precision low-power applications; however, slew rate (0.2 V/µs) is reduced.

Moisture Sensitivity Levels: The OPA124U specifies MSL 3 (168 hours). Substitute parts offer improved moisture handling: OPA145ID (MSL 2, 1 year), AD825ARZ variants (MSL 1, unlimited), and LT1008S8 variants (MSL 1, unlimited), reducing storage and handling constraints.

Frequently Asked Questions (FAQ)

Q: Can the OPA145ID directly replace the OPA124U in existing designs?

A: The OPA145ID shares the 8-SOIC package and supply voltage range (4.5V to 36V), providing mechanical and electrical compatibility. However, the OPA145ID is a J-FET amplifier with superior performance characteristics (20 V/µs slew rate, 5.5 MHz bandwidth, rail-to-rail output). Designs relying on specific OPA124U general-purpose characteristics should be evaluated for functional equivalence before substitution.

Q: What is the primary difference between AD825ARZ, AD825ARZ-REEL, and AD825ARZ-REEL7?

A: These three part numbers are electrically identical J-FET amplifiers with identical electrical specifications (140 V/µs slew rate, 26 MHz bandwidth, 50 mA output current). The differences are packaging configurations: AD825ARZ is supplied in tube packaging, AD825ARZ-REEL in cut tape with Digi-Reel®, and AD825ARZ-REEL7 in cut tape with Digi-Reel® (7-inch reel). Selection depends on procurement and assembly requirements.

Q: Why do the LT1008S8#PBF and LT1008S8#TRPBF have different slew rates than the OPA124U?

A: The LT1008S8 variants are general-purpose amplifiers optimized for precision and low-power operation (380 µA supply current, 30 µV input offset voltage). The reduced slew rate (0.2 V/µs) reflects this design focus on accuracy rather than speed. These parts are suitable for applications where precision and power efficiency outweigh dynamic performance requirements.

Q: Are all substitute parts suitable for the full -25°C to 85°C operating temperature range of the OPA124U?

A: No. The OPA145ID extends the range to -40°C to 125°C. The AD825ARZ variants operate -40°C to 85°C, matching the OPA124U upper limit. The LT1008S8 variants operate 0°C to 70°C, which is narrower than the OPA124U specification. Temperature range compatibility must be verified for specific applications.

Q: What is the significance of the 1 pA input bias current specification of the OPA124U?

A: The 1 pA input bias current is exceptionally low, characteristic of Difet® technology. Substitute parts show higher input bias currents: OPA145ID (2 pA), AD825ARZ variants (15 pA), and LT1008S8 variants (100 pA). Applications requiring ultra-low input bias current for high-impedance signal sources should prioritize the OPA145ID or AD825ARZ variants over the LT1008S8 options.

Q: Can the AD825ARZ variants be used in applications requiring the OPA124U's 1.5 MHz gain-bandwidth product?

A: Yes. The AD825ARZ variants provide 26 MHz bandwidth, significantly exceeding the 1.5 MHz requirement. However, the higher bandwidth and slew rate (140 V/µs) may introduce increased noise and stability considerations in applications designed for the OPA124U's lower bandwidth. Circuit stability analysis is recommended for bandwidth-sensitive designs.

Q: What packaging options are available for high-volume production?

A: For high-volume assembly, the AD825ARZ-REEL and AD825ARZ-REEL7 offer cut tape and Digi-Reel® packaging suitable for automated pick-and-place equipment. The LT1008S8#TRPBF provides tape and reel packaging. The OPA145ID is supplied in tube packaging. Packaging selection should align with assembly line capabilities and procurement volume requirements.

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