OPA124U/2K5 Equivalent & Substitute Parts

Part Overview

The OPA124U/2K5 is a general-purpose operational amplifier manufactured by Texas Instruments in the Difet® series. This device is packaged in 8-SOIC surface-mount configuration and is classified as obsolete. The OPA124U/2K5 operates across a wide supply voltage range (10V to 36V) with low input bias current (1 pA) and moderate slew rate (1.6V/µs), making it suitable for precision analog signal conditioning applications.

Due to its obsolete product status, equivalent and substitute parts are necessary for ongoing production, maintenance, and new design implementations. Substitute components must maintain electrical compatibility within the specified parameter tolerances and physical compatibility with the 8-SOIC package footprint.

Key Parameters

Parameter	OPA124U/2K5 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°C to 85°C	—
Package / Case	8-SOIC (0.154", 3.90mm Width)	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level	3 (168 Hours)	—

Substitute Part Grouping Explanation

Substitution of the OPA124U/2K5 is determined by the following critical parameters:

Mechanical Compatibility: All substitute parts must use the 8-SOIC (0.154", 3.90mm Width) package with surface-mount configuration to ensure PCB footprint compatibility.

Electrical Compatibility: Substitute parts must operate within the supply voltage range of 10V to 36V minimum and maximum specifications. The input bias current, input offset voltage, slew rate, and gain bandwidth product define the functional performance envelope. Parts with superior specifications (lower input bias current, lower offset voltage, higher slew rate, higher bandwidth) are acceptable substitutes provided they maintain backward compatibility in the application circuit.

Regulatory Compliance: All substitute parts must maintain ROHS3 compliance and REACH unaffected status to satisfy environmental and regulatory requirements.

Product Status Consideration: Active product status is preferred for long-term availability and supply chain stability, though the original part is obsolete.

The substitute parts are grouped into two categories based on amplifier type:

Category 1 - J-FET Amplifiers (Enhanced Performance): OPA145IDR, AD825ARZ, AD825ARZ-REEL, and AD825ARZ-REEL7 offer superior electrical performance with higher slew rates, higher gain bandwidth products, and lower input offset voltages compared to the original general-purpose design.

Category 2 - General Purpose Amplifiers (Functional Equivalence): LT1008S8#PBF and LT1008S8#TRPBF maintain the general-purpose amplifier classification with compatible supply voltage ranges and package configuration.

Parameter Comparison

Parameter	OPA124U/2K5	OPA145IDR	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	-55 to 150	-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	—
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	—
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	—
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	—

Engineering Selection Recommendations

For Direct Functional Replacement with Enhanced Performance:

The OPA145IDR (Texas Instruments, J-FET amplifier) is the manufacturer-recommended substitute. It maintains the 8-SOIC package, operates across the full 4.5V to 36V supply range, and is classified as active product status. The OPA145IDR provides superior slew rate (20V/µs versus 1.6V/µs), higher gain bandwidth product (5.5 MHz versus 1.5 MHz), and lower input offset voltage (40 µV versus 200 µV). The rail-to-rail output capability extends application flexibility. Operating temperature range extends to -55°C to 150°C, providing broader environmental coverage.

For High-Speed Applications:

The AD825ARZ, AD825ARZ-REEL, and AD825ARZ-REEL7 (Analog Devices Inc., J-FET amplifiers) deliver significantly enhanced performance with slew rate of 140V/µs and gain bandwidth product of 26 MHz. These parts are suitable for applications requiring high-speed signal processing. All three variants share identical electrical specifications and differ only in packaging format (Tube, Cut Tape & Digi-Reel®, or Cut Tape & Digi-Reel® with 7-inch reel). The AD825ARZ-REEL7 offers the highest inventory availability (18,103 pieces). Minimum supply voltage is 10V, matching the original specification. Moisture sensitivity level is 1 (Unlimited), providing superior handling characteristics compared to the original MSL 3 rating.

For Low-Power, General-Purpose Applications:

The LT1008S8#PBF and LT1008S8#TRPBF (Analog Devices Inc., general-purpose amplifiers) maintain the general-purpose amplifier classification with significantly reduced supply current (380 µA versus 2.5 mA). These parts are suitable for battery-powered or low-power applications. Operating temperature range is 0°C to 70°C, which is narrower than the original. Minimum supply voltage is 4V, providing lower voltage operation capability. Slew rate is reduced to 0.2V/µs, suitable only for low-frequency applications. Moisture sensitivity level is 1 (Unlimited).

Compliance and Availability:

All substitute parts maintain ROHS3 compliance and REACH unaffected status. All substitute parts are classified as active product status, ensuring long-term availability and supply chain continuity. Current inventory levels range from 1,221 to 18,103 pieces across all substitute options.

Frequently Asked Questions (FAQ)

Q1: Can the OPA145IDR directly replace the OPA124U/2K5 without circuit modifications?

A: The OPA145IDR is mechanically and electrically compatible with the OPA124U/2K5 in the 8-SOIC package. Both operate across overlapping supply voltage ranges (OPA145IDR: 4.5V to 36V; OPA124U/2K5: 10V to 36V). The OPA145IDR provides superior electrical performance with higher slew rate and gain bandwidth product. Circuit modifications are not required for basic substitution, though application-specific circuit optimization may be beneficial to utilize the enhanced performance characteristics.

Q2: What is the difference between AD825ARZ, AD825ARZ-REEL, and AD825ARZ-REEL7?

A: These three parts are electrically identical J-FET amplifiers from Analog Devices Inc. The differences are packaging and delivery format only. AD825ARZ is supplied in Tube packaging. AD825ARZ-REEL and AD825ARZ-REEL7 are both supplied in Cut Tape & Digi-Reel® format, with AD825ARZ-REEL7 using 7-inch reels. All three share identical electrical specifications, operating temperature range (-40°C to 85°C), and compliance certifications. Selection between these variants depends on assembly equipment compatibility and inventory management requirements.

Q3: Why does the LT1008S8#PBF have lower slew rate than the original OPA124U/2K5?

A: The LT1008S8#PBF is optimized for low-power operation with supply current of 380 µA compared to 2.5 mA in the OPA124U/2K5. This design trade-off results in reduced slew rate (0.2V/µs versus 1.6V/µs). The LT1008S8#PBF is suitable for applications where power consumption is critical and signal bandwidth requirements are modest (below approximately 100 kHz). For high-frequency applications, the AD825ARZ or OPA145IDR are more appropriate selections.

Q4: Are all substitute parts compatible with the original 8-SOIC PCB footprint?

A: Yes. All substitute parts use the 8-SOIC (0.154", 3.90mm Width) package with surface-mount configuration. PCB footprint compatibility is guaranteed across all substitute options. No PCB redesign is required for mechanical substitution.

Q5: What is the significance of Moisture Sensitivity Level (MSL) differences?

A: The original OPA124U/2K5 has MSL 3 (168 Hours), requiring moisture bake-out procedures before reflow soldering if the component has been exposed to ambient humidity for extended periods. The substitute parts have MSL 1 (Unlimited) or MSL 2 (1 Year), providing more relaxed moisture handling requirements. MSL 1 components require no moisture control measures. This represents an improvement in manufacturing and assembly process flexibility.

Q6: Which substitute part offers the widest operating temperature range?

A: The OPA145IDR offers the widest operating temperature range of -55°C to 150°C, compared to the original OPA124U/2K5 range of -25°C to 85°C. This extended range is suitable for industrial and automotive applications requiring operation across extreme temperature environments. The AD825ARZ variants operate from -40°C to 85°C, and the LT1008S8 variants operate from 0°C to 70°C.

Q7: What is the primary advantage of J-FET amplifiers (OPA145IDR, AD825ARZ series) over general-purpose amplifiers?

A: J-FET amplifiers feature extremely low input bias current (2 pA to 15 pA) compared to general-purpose designs (100 pA in LT1008S8). This characteristic is critical for high-impedance signal sources and precision measurement applications where input bias current can introduce significant measurement errors. J-FET amplifiers also typically offer higher slew rates and gain bandwidth products, enabling faster signal processing.

Q8: Is the OPA124U/2K5 still available for purchase?

A: The OPA124U/2K5 is classified as obsolete product status. Current inventory of 4,479 pieces is available from existing stock, but no new manufacturing is occurring. For new designs or long-term production requirements, selection of an active substitute part (OPA145IDR, AD825ARZ series, or LT1008S8 series) is recommended to ensure supply chain continuity.

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