OPA128KM Equivalent & Substitute Parts

Part Overview

The OPA128KM is a general-purpose operational amplifier manufactured by Texas Instruments in a TO-99-8 metal can package. This device features JFET input technology with a 1 MHz gain-bandwidth product and operates across a 10V to 36V supply range. The OPA128KM is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements. Substitute parts must maintain compatibility with the original electrical specifications and mechanical form factor while offering improved availability and potentially enhanced performance characteristics.

Substiute Parts

OPA128KM

Texas InstrumentsIn Stock: 2341OPA128KM Datasheet

Current PartRFQ

OPA145ID

Texas InstrumentsIn Stock: 2413OPA145ID Datasheet

MFR RecommendedRFQ

AD549LHZ

Analog Devices Inc.In Stock: 1281AD549LHZ Datasheet

MFR RecommendedRFQ

AD549SH/883B

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

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the OPA128KM are grouped based on strict electrical and mechanical compatibility criteria. The primary substitution logic is determined by the following parameters:

Package Compatibility: The OPA128KM uses a TO-99-8 metal can through-hole package. Direct mechanical substitutes must use the same package type to ensure PCB compatibility without layout modifications.

Electrical Performance Envelope: Substitute parts must operate within the supply voltage range of 10V to 36V and maintain single-circuit amplifier topology. The slew rate (3V/µs) and gain-bandwidth product (1 MHz) define the performance class.

Input Bias Current Specification: The OPA128KM specifies 0.075 pA input bias current, characteristic of JFET input amplifiers. Substitutes with equal or lower input bias current maintain compatibility with high-impedance signal sources.

Output Current Capability: The 10 mA output current per channel establishes the minimum load-driving capability required for functional equivalence.

Compliance Requirements: All substitute parts must maintain ROHS3 compliance and EAR99 export classification to ensure regulatory alignment with the original part.

Parameter Comparison

Engineering Selection Recommendations

Direct Package Substitutes (TO-99-8 Metal Can):

The AD549LHZ and AD549SH/883B are direct mechanical and electrical substitutes for the OPA128KM. Both parts maintain the TO-99-8 through-hole package, identical supply voltage range (10V to 36V), and equivalent slew rate and gain-bandwidth product specifications. The AD549LHZ is classified as active product status with commercial temperature range (0°C to 70°C), matching the original OPA128KM operating conditions. The AD549SH/883B extends the operating temperature range to -55°C to 125°C and includes MIL-STD-883 military qualification, suitable for applications requiring extended temperature performance or military-grade reliability. Both AD549 variants demonstrate lower input bias current (0.04 pA for AD549LHZ) compared to the OPA128KM specification, providing improved performance in high-impedance applications.

Alternative Topology Substitute (Surface Mount):

The OPA145ID represents a performance-enhanced alternative with different package technology. This part uses an 8-SOIC surface-mount package rather than through-hole, requiring PCB layout redesign. The OPA145ID offers superior electrical performance with 20V/µs slew rate and 5.5 MHz gain-bandwidth product, along with extended operating temperature range (-40°C to 125°C) and rail-to-rail output capability. This substitute is appropriate for new designs where surface-mount assembly is standard practice and enhanced performance is beneficial. The OPA145ID is not suitable for direct board-level replacement of existing OPA128KM installations due to package incompatibility.

Compliance and Availability:

All substitute parts maintain ROHS3 compliance and EAR99 export classification, ensuring regulatory alignment. The AD549LHZ and AD549SH/883B offer the highest compatibility for direct replacement applications. Selection between these two AD549 variants depends on temperature range requirements: use AD549LHZ for standard commercial applications and AD549SH/883B for extended or military temperature specifications.

Frequently Asked Questions (FAQ)

Q: Can the OPA145ID directly replace the OPA128KM on an existing PCB?

A: No. The OPA145ID uses an 8-SOIC surface-mount package, while the OPA128KM uses a TO-99-8 through-hole metal can package. Direct board-level replacement is not possible without PCB redesign and assembly process changes. The OPA145ID is suitable only for new designs incorporating surface-mount assembly.

Q: What is the primary difference between AD549LHZ and AD549SH/883B?

A: Both parts use identical TO-99-8 packages and share the same electrical specifications. The AD549SH/883B includes MIL-STD-883 military qualification and operates across an extended temperature range (-55°C to 125°C) compared to the AD549LHZ commercial range (0°C to 70°C). Select AD549SH/883B for military applications or systems requiring operation beyond standard commercial temperature limits.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. The OPA128KM, OPA145ID, AD549LHZ, and AD549SH/883B are all ROHS3 compliant and maintain EAR99 export classification, ensuring regulatory compatibility across all substitute options.

Q: How do the input bias current specifications affect circuit design?

A: The OPA128KM specifies 0.075 pA input bias current. The AD549LHZ provides 0.04 pA, offering improved performance in high-impedance signal conditioning applications. The OPA145ID specifies 2 pA, which is higher but remains suitable for most general-purpose amplifier applications. Lower input bias current reduces offset errors in transimpedance and precision measurement circuits.

Q: What is the significance of the moisture sensitivity level difference between OPA145ID and other substitutes?

A: The OPA128KM, AD549LHZ, and AD549SH/883B all specify MSL 1 (Unlimited), indicating no moisture sensitivity restrictions during storage and handling. The OPA145ID specifies MSL 2 (1 Year), requiring controlled humidity storage and limiting shelf life to one year from manufacturing. This difference affects supply chain management and component storage protocols for the OPA145ID.

Q: Can the OPA145ID be used in applications requiring the full 10V to 36V supply range?

A: The OPA145ID operates across a 4.5V to 36V supply range, which encompasses the OPA128KM specification of 10V to 36V. However, the OPA145ID can also operate at lower supply voltages (4.5V minimum) not supported by the OPA128KM. For applications strictly requiring 10V minimum supply, both parts are compatible.

Q: Which substitute part offers the best direct replacement for legacy equipment?

A: The AD549LHZ provides the best direct replacement for legacy OPA128KM installations. It maintains identical package type (TO-99-8 through-hole), matching supply voltage range, equivalent performance specifications, and commercial temperature range. No PCB modifications are required for this substitution.