OPA128SM Equivalent & Substitute Parts

Part Overview

The OPA128SM is a general-purpose operational amplifier manufactured by Texas Instruments in the Difet® series. This device is packaged in a TO-99-8 metal can configuration and is designed for single-circuit amplification applications. The OPA128SM is classified as obsolete, making equivalent and substitute parts necessary for new designs and production continuity. The part operates across a wide temperature range of -55°C to 125°C and supports supply voltages from 10V to 36V, making it suitable for industrial and military applications.

Substiute Parts

OPA128SM

Texas InstrumentsIn Stock: 2005OPA128SM Datasheet

Current PartRFQ

OPA145ID

Texas InstrumentsIn Stock: 2413OPA145ID Datasheet

MFR RecommendedRFQ

AD549SH/883B

Analog Devices Inc.In Stock: 1386AD549SH/883B Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the OPA128SM is determined by electrical and mechanical compatibility across the following critical parameters:

Electrical Compatibility Criteria:

• Amplifier type classification (General Purpose or J-FET)
• Slew rate and gain bandwidth product performance
• Input bias current and input offset voltage specifications
• Supply current consumption
• Output current capability per channel
• Supply voltage range (minimum 10V to maximum 36V)
• Operating temperature range (-55°C to 125°C minimum)

Mechanical Compatibility Criteria:

• Package type and form factor
• Mounting technology (through-hole or surface mount)
• Pin configuration and circuit count (single circuit)

Compliance and Status Criteria:

• RoHS3 compliance
• Product status (active preferred for new designs; obsolete acceptable for legacy support)
• Military qualification where applicable

Two substitute parts are identified for the OPA128SM:

1. OPA145ID — Active-status J-FET amplifier with enhanced performance characteristics, surface-mount packaging, and rail-to-rail output capability. Suitable for designs requiring improved slew rate and bandwidth with modern packaging.

2. AD549SH/883B — Active-status general-purpose amplifier with military-grade qualification (MIL-STD-883), through-hole TO-99-8 packaging matching the original form factor. Suitable for legacy designs and military applications requiring direct package compatibility.

Parameter Comparison

Engineering Selection Recommendations

For Direct Package Replacement (Through-Hole TO-99-8):

Select AD549SH/883B when the design requires mechanical and electrical compatibility with the original OPA128SM footprint. This substitute maintains the through-hole TO-99-8 metal can package, identical supply voltage range (10V to 36V), and matching operating temperature span (-55°C to 125°C). The AD549SH/883B is active-status and carries MIL-STD-883 military qualification, providing enhanced reliability for legacy systems and military applications. Input bias current and slew rate are identical to the OPA128SM. Supply current is reduced (600µA versus 900µA), and output current capability is doubled (20mA versus 10mA).

For Performance Enhancement with Modern Packaging:

Select OPA145ID when the design can accommodate surface-mount technology and benefits from improved electrical performance. The OPA145ID offers significantly higher slew rate (20V/µs versus 3V/µs) and gain bandwidth product (5.5MHz versus 1MHz), with superior input offset voltage (40µV versus 140µV). This J-FET amplifier provides rail-to-rail output capability and operates at lower supply current (445µA). The minimum supply voltage is reduced to 4.5V, expanding application flexibility. The OPA145ID is active-status and ROHS3 compliant. Note that the operating temperature minimum is -40°C (versus -55°C for the OPA128SM) and input bias current is higher (2pA versus 0.075pA).

Compliance Verification:

All three parts (OPA128SM, OPA145ID, AD549SH/883B) are ROHS3 compliant and REACH unaffected, meeting modern environmental and regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can OPA145ID directly replace OPA128SM in existing PCB designs?

A: No. The OPA145ID uses 8-SOIC surface-mount packaging, while the OPA128SM uses through-hole TO-99-8 metal can packaging. PCB layout and footprint modifications are required. For direct PCB compatibility without redesign, use AD549SH/883B.

Q: What is the key difference between OPA145ID and AD549SH/883B as substitutes?

A: OPA145ID is a J-FET amplifier with enhanced performance (higher slew rate and bandwidth) in modern surface-mount packaging. AD549SH/883B is a general-purpose amplifier with identical electrical characteristics to OPA128SM, packaged in the original through-hole TO-99-8 form factor and qualified to MIL-STD-883 military standards.

Q: Is the OPA145ID suitable for applications requiring -55°C minimum operating temperature?

A: No. The OPA145ID operates from -40°C to 125°C. For applications requiring -55°C operation, use AD549SH/883B, which maintains the -55°C to 125°C range of the OPA128SM.

Q: Does the lower supply current of OPA145ID affect circuit performance?

A: The OPA145ID consumes 445µA versus 900µA for the OPA128SM, representing reduced power dissipation. This is a performance advantage, not a limitation. The lower current consumption does not compromise amplifier functionality.

Q: Can AD549SH/883B be used in new designs, or is it only for legacy applications?

A: AD549SH/883B is active-status and fully compliant with current standards (ROHS3, REACH unaffected). It is suitable for both legacy replacement and new designs, particularly those requiring through-hole packaging or military-grade qualification.

Q: What is the significance of MIL-STD-883 qualification on the AD549SH/883B?

A: MIL-STD-883 qualification indicates the part meets military-grade reliability and testing standards. This qualification is relevant for aerospace, defense, and high-reliability industrial applications. The OPA128SM and OPA145ID do not carry this qualification.

Q: Are all three parts RoHS3 compliant?

A: Yes. The OPA128SM, OPA145ID, and AD549SH/883B are all ROHS3 compliant and REACH unaffected, meeting environmental and regulatory requirements for commercial and industrial applications.

Q: What is the impact of the OPA145ID's rail-to-rail output on circuit design?

A: Rail-to-rail output capability allows the amplifier output to swing closer to the supply rails, maximizing the usable output voltage range. This is an enhancement over the OPA128SM and AD549SH/883B, which do not specify rail-to-rail output. Designs can benefit from increased dynamic range without circuit modification.