LM6181IM-8 Equivalent & Substitute Parts

Part Overview

The LM6181IM-8 is a Current Feedback Amplifier manufactured by Texas Instruments, housed in an 8-SOIC surface mount package. This device is classified as obsolete, indicating discontinued production and limited availability for new designs. The LM6181IM-8 delivers high-speed amplification with a 2000V/µs slew rate and 100 MHz bandwidth, suitable for applications requiring current feedback topology. Due to its obsolete status, identifying functionally equivalent substitute parts is essential for design continuity and procurement planning.

Substiute Parts

LM6181IM-8

Texas InstrumentsIn Stock: 6344LM6181IM-8 Datasheet

Current PartRFQ

ISL28177FBZ

Renesas Electronics CorporationIn Stock: 1367ISL28177FBZ Datasheet

MFR RecommendedRFQ

ISL28177FBZ-T13

Renesas Electronics CorporationIn Stock: 2530ISL28177FBZ-T13 Datasheet

MFR RecommendedRFQ

ISL28177FBZ-T7

Renesas Electronics CorporationIn Stock: 1925ISL28177FBZ-T7 Datasheet

MFR RecommendedRFQ

OPA691ID

Texas InstrumentsIn Stock: 1687OPA691ID Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the LM6181IM-8 is determined by the following critical parameters:

Topology Match: Amplifier type (Current Feedback vs. General Purpose) is the primary classification criterion. The LM6181IM-8 employs current feedback architecture, which differs fundamentally from general purpose operational amplifiers.

Package Compatibility: All substitute candidates must use the 8-SOIC surface mount package with identical physical dimensions (0.154", 3.90mm Width) to ensure PCB layout compatibility without redesign.

Electrical Performance Envelope: Substitutes must operate within the supply voltage range (minimum 7V to maximum 32V for the main part) and support the operating temperature range (-40°C to 85°C).

Performance Characteristics: Slew rate, bandwidth, and output current capability define the performance class. The LM6181IM-8 specifies 2000V/µs slew rate and 100 MHz bandwidth.

Based on these criteria, substitute parts are grouped as follows:

Group 1 - Current Feedback Topology (Direct Functional Equivalent): OPA691ID maintains current feedback architecture with enhanced performance specifications and active product status.

Group 2 - General Purpose Topology (Functional Alternative): ISL28177FBZ, ISL28177FBZ-T13, and ISL28177FBZ-T7 employ general purpose amplifier topology. These parts operate within compatible supply ranges and package specifications but differ in amplifier architecture and performance characteristics.

Parameter Comparison

Engineering Selection Recommendations

OPA691ID Selection Criteria:

The OPA691ID is the primary substitute for applications requiring current feedback amplifier topology. This device maintains architectural compatibility with the LM6181IM-8 while offering active product status and ROHS3 compliance. The OPA691ID delivers superior performance with 2100V/µs slew rate and 280 MHz bandwidth. However, the maximum supply voltage is limited to 12V compared to the LM6181IM-8's 32V maximum, requiring verification of circuit supply requirements. Output current capability increases to 190 mA, exceeding the original 130 mA specification. The operating temperature range remains -40°C to 85°C, matching the original device.

ISL28177 Series Selection Criteria:

The ISL28177FBZ, ISL28177FBZ-T13, and ISL28177FBZ-T7 are functionally equivalent in packaging and general electrical compatibility but employ general purpose amplifier topology rather than current feedback architecture. These devices are suitable for applications where current feedback characteristics are not essential to circuit function. All three variants share identical electrical specifications and differ only in packaging format (Tube vs. Tape & Reel). The ISL28177 series provides superior compliance status (ROHS3 compliant) and extended operating temperature range (-40°C to 125°C). Supply voltage range extends to 40V maximum, accommodating higher voltage applications. Input bias current is significantly lower at 200 pA, and input offset voltage is reduced to 150 µV. Output current capability is limited to 30 mA, which may restrict applications requiring higher drive capability.

Compliance and Availability:

All substitute parts carry active product status, ensuring long-term availability and supply chain stability. The ISL28177 series and OPA691ID are ROHS3 compliant, addressing environmental and regulatory requirements. Inventory levels are adequate across all substitute options, with ISL28177FBZ-T13 offering the highest stock position at 2482 pieces.

Frequently Asked Questions (FAQ)

Q: Can the ISL28177 series directly replace the LM6181IM-8 in existing designs?

A: The ISL28177 series shares the 8-SOIC package and operates within compatible supply voltage ranges. However, the amplifier topology differs fundamentally. The LM6181IM-8 uses current feedback architecture, while the ISL28177 series employs general purpose topology. Direct substitution is possible only if the circuit design does not depend on current feedback characteristics. Circuit simulation and functional testing are necessary to confirm compatibility.

Q: What is the primary advantage of the OPA691ID over the ISL28177 series?

A: The OPA691ID maintains current feedback amplifier topology, matching the LM6181IM-8's architecture. This ensures functional equivalence for circuits specifically designed around current feedback characteristics. The OPA691ID also delivers higher bandwidth (280 MHz vs. 100 MHz) and greater output current (190 mA vs. 130 mA). The primary limitation is the reduced maximum supply voltage (12V vs. 32V).

Q: Are there packaging differences between ISL28177FBZ, ISL28177FBZ-T13, and ISL28177FBZ-T7?

A: All three variants use identical 8-SOIC packages with the same physical dimensions. The differences are in shipping and handling formats: ISL28177FBZ ships in Tube packaging, while ISL28177FBZ-T13 and ISL28177FBZ-T7 ship in Tape & Reel format. Electrical specifications and performance characteristics are identical across all three variants.

Q: Does the LM6181IM-8's RoHS non-compliance affect substitute selection?

A: If the application or end-use market requires RoHS compliance, all substitute parts (OPA691ID, ISL28177FBZ, ISL28177FBZ-T13, ISL28177FBZ-T7) are ROHS3 compliant and satisfy regulatory requirements. For legacy systems or applications without compliance mandates, RoHS status is not a selection factor.

Q: What supply voltage considerations apply when substituting with OPA691ID?

A: The OPA691ID maximum supply voltage is 12V, compared to the LM6181IM-8's 32V maximum. Circuits operating at supply voltages above 12V cannot use the OPA691ID without redesign. Verify the circuit's actual supply voltage requirement before selecting this substitute.

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

A: The LM6181IM-8 specifies 5 µA input bias current. The OPA691ID increases this to 15 µA, while the ISL28177 series reduces it to 200 pA. Higher input bias current may affect precision circuits with high-impedance inputs. Lower input bias current improves performance in sensitive applications. Circuit design must account for these differences in input impedance and bias current compensation.

Q: Can the ISL28177 series operate at the LM6181IM-8's full temperature range?

A: The ISL28177 series extends the operating temperature range to -40°C to 125°C, exceeding the LM6181IM-8's -40°C to 85°C specification. This provides additional margin for high-temperature applications. The LM6181IM-8's temperature range is fully contained within the ISL28177 specification.