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INA125U/2K5 Equivalent & Substitute Parts
Part Overview
The INA125U/2K5 is an instrumentation amplifier manufactured by Texas Instruments, housed in a 16-SOIC package. This single-circuit device operates across a supply voltage range of 2.7V to 36V and is designed for precision signal conditioning applications requiring low input offset voltage and low input bias current. The part maintains Active product status with full RoHS3 compliance and REACH unaffected designation. Substitute parts are identified when design requirements necessitate alternative packaging formats, enhanced performance specifications, or different thermal operating ranges while maintaining functional compatibility within the instrumentation amplifier category.
Substiute Parts
Key Parameters
| Parameter | Value | Unit |
|---|---|---|
| Amplifier Type | Instrumentation | — |
| Number of Circuits | 1 | — |
| Slew Rate | 0.2 | V/µs |
| -3dB Bandwidth | 150 | kHz |
| Current - Input Bias | 10 | nA |
| Voltage - Input Offset | 50 | µV |
| Current - Supply | 460 | µA |
| Current - Output / Channel | 12 | mA |
| Voltage - Supply Span (Min) | 2.7 | V |
| Voltage - Supply Span (Max) | 36 | V |
| Operating Temperature | -40 to 85 | °C |
| Mounting Type | Surface Mount | — |
| Package / Case | 16-SOIC (0.154", 3.90mm Width) | — |
| RoHS Status | ROHS3 Compliant | — |
| Moisture Sensitivity Level | 3 (168 Hours) | — |
Substitute Part Grouping Explanation
Substitution of the INA125U/2K5 is determined by the following criteria:
Primary Compatibility Factors:
- Amplifier Type: Instrumentation (single circuit)
- Supply Voltage Range: Minimum 2.7V to Maximum 36V overlap required
- Operating Temperature: -40°C to 85°C baseline
- Surface Mount technology
- RoHS3 compliance and REACH unaffected status
Substitution Logic: Substitute parts are grouped by package format (8-SOIC, 8-MSOP) and performance tier. The INA125U/2K5 operates at lower bandwidth (150 kHz) and lower slew rate (0.2V/µs) with moderate supply current (460µA). Substitute devices from Analog Devices Inc. maintain the instrumentation amplifier topology and core compliance requirements. Substitutes with enhanced specifications (higher bandwidth, faster slew rate, lower input bias current) are functionally compatible for applications where the INA125U/2K5 performance envelope is sufficient. Package downsizing from 16-SOIC to 8-SOIC or 8-MSOP is permitted when board layout constraints require smaller footprints.
Key Parameters for Substitution Assessment:
- Supply voltage range overlap (minimum 2.7V to 36V)
- Input offset voltage (50µV baseline)
- Input bias current (10nA baseline)
- Operating temperature range (-40°C to 85°C minimum)
- Compliance certifications (RoHS3, REACH)
Parameter Comparison
| Parameter | INA125U/2K5 | AD8225ARZ | AD8421ARMZ-RL | AD8421ARZ | AD8421ARZ-R7 | AD8421ARZ-RL | AD8421BRMZ | AD8421BRMZ-R7 | AD8421BRZ | AD8421BRZ-R7 | AD8421TRMZ-EP |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Manufacturer | Texas Instruments | Analog Devices Inc. | Analog Devices Inc. | Analog Devices Inc. | Analog Devices Inc. | Analog Devices Inc. | Analog Devices Inc. | Analog Devices Inc. | Analog Devices Inc. | Analog Devices Inc. | Analog Devices Inc. |
| Amplifier Type | Instrumentation | Instrumentation | Instrumentation | Instrumentation | Instrumentation | Instrumentation | Instrumentation | Instrumentation | Instrumentation | Instrumentation | Instrumentation |
| Number of Circuits | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Slew Rate (V/µs) | 0.2 | 5 | 35 | 35 | 35 | 35 | 35 | 35 | 35 | 35 | 35 |
| -3dB Bandwidth (kHz) | 150 | 900 | 10000 | 10000 | 10000 | 10000 | 10000 | 10000 | 10000 | 10000 | 10000 |
| Current - Input Bias (nA) | 10 | 0.5 | 1 | 1 | 1 | 1 | 0.1 | 0.1 | 0.1 | 0.1 | 1 |
| Voltage - Input Offset (µV) | 50 | 50 | 60 | 60 | 60 | 60 | 25 | 25 | 25 | 25 | 70 |
| Current - Supply (mA) | 0.46 | 1.05 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 |
| Current - Output / Channel (mA) | 12 | 18 | 65 | 65 | 65 | 65 | 65 | 65 | 65 | 65 | 65 |
| Voltage - Supply Span Min (V) | 2.7 | 3.4 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 |
| Voltage - Supply Span Max (V) | 36 | 36 | 36 | 36 | 36 | 36 | 36 | 36 | 36 | 36 | 36 |
| Operating Temperature (°C) | -40 to 85 | -40 to 85 | -40 to 85 | -40 to 85 | -40 to 85 | -40 to 85 | -40 to 85 | -40 to 85 | -40 to 85 | -40 to 85 | -55 to 125 |
| Package / Case | 16-SOIC | 8-SOIC | 8-MSOP | 8-SOIC | 8-SOIC | 8-SOIC | 8-MSOP | 8-MSOP | 8-SOIC | 8-SOIC | 8-MSOP |
| RoHS Status | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant |
| Moisture Sensitivity Level | 3 (168 Hours) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) |
Engineering Selection Recommendations
Compliance and Certification Basis:
All substitute parts maintain Active product status and RoHS3 compliance. The INA125U/2K5 carries Moisture Sensitivity Level 3 (168 hours), while all Analog Devices substitutes feature MSL 1 (Unlimited), providing superior moisture tolerance for storage and handling.
Supply Voltage Consideration:
The INA125U/2K5 operates from 2.7V minimum supply voltage. Most Analog Devices substitutes require 5V minimum supply voltage (AD8421 series, AD8225ARZ). Applications requiring operation below 5V are limited to the original INA125U/2K5 or require circuit redesign with alternative power supply architecture.
Thermal Operating Range:
Standard substitutes (AD8225ARZ, AD8421 variants) operate -40°C to 85°C, matching the INA125U/2K5 baseline. The AD8421TRMZ-EP extends the upper temperature limit to 125°C, suitable for extended industrial temperature applications.
Package Format Selection:
- 8-SOIC format (AD8225ARZ, AD8421ARZ, AD8421ARZ-R7, AD8421BRZ, AD8421BRZ-R7): Maintains 0.154" width, compatible with standard SOIC footprints. Reduces pin count from 16 to 8.
- 8-MSOP format (AD8421ARMZ-RL, AD8421BRMZ, AD8421BRMZ-R7, AD8421TRMZ-EP): Compact 0.118" width for space-constrained layouts.
Performance Tier Matching:
- Lower performance tier (AD8225ARZ): 900 kHz bandwidth, 5V/µs slew rate. Suitable for general-purpose instrumentation applications.
- Higher performance tier (AD8421 series): 10 MHz bandwidth, 35V/µs slew rate, enhanced output current (65mA). Required for high-speed signal conditioning and low-impedance load driving.
Frequently Asked Questions (FAQ)
Q: Can the INA125U/2K5 be directly replaced with an 8-pin AD8421 variant on the same PCB?
A: No. The INA125U/2K5 uses a 16-pin SOIC package while AD8421 variants use 8-pin SOIC or 8-pin MSOP packages. PCB layout redesign is required. Pin-to-pin functional mapping must be verified against device datasheets, as internal circuit topology differs between the 16-pin and 8-pin configurations.
Q: What is the minimum supply voltage requirement for substitution?
A: The INA125U/2K5 operates from 2.7V. Most Analog Devices substitutes (AD8421 series, AD8225ARZ) require 5V minimum. If your application uses 2.7V to 5V supply voltage, the INA125U/2K5 is the only option from this substitute list.
Q: Are all substitute parts RoHS3 compliant?
A: Yes. All listed substitute parts carry RoHS3 Compliant designation and REACH Unaffected status, matching the compliance profile of the INA125U/2K5.
Q: What is the difference between AD8421ARZ and AD8421ARZ-R7?
A: Both parts are electrically identical 8-SOIC instrumentation amplifiers with identical specifications. The difference is packaging format: AD8421ARZ ships in Tube packaging, while AD8421ARZ-R7 ships in Cut Tape (CT) & Digi-Reel® format. Selection depends on assembly line requirements and inventory management preferences.
Q: Why do AD8421BRMZ variants have lower input offset voltage (25µV) compared to AD8421ARMZ variants (60µV)?
A: The "B" grade designation indicates tighter input offset voltage specification (25µV maximum versus 60µV). This represents a higher precision grade within the AD8421 product family. Selection depends on application accuracy requirements.
Q: Can I use AD8421TRMZ-EP in a -40°C to 85°C application?
A: Yes. The AD8421TRMZ-EP operates across -55°C to 125°C, which encompasses the -40°C to 85°C range. The extended temperature rating provides additional margin for thermal stress conditions without performance degradation within the standard operating range.
Q: What is the impact of higher slew rate on circuit performance?
A: The INA125U/2K5 has 0.2V/µs slew rate, while AD8421 substitutes provide 35V/µs. Higher slew rate enables faster signal settling and reduced distortion for high-frequency input signals. For low-frequency applications (below 150 kHz), the difference is not functionally significant. For applications requiring bandwidth above 150 kHz, higher slew rate substitutes are necessary.
Q: Are there any moisture sensitivity concerns when substituting?
A: The INA125U/2K5 carries MSL 3 (168 hours), requiring controlled storage conditions. All Analog Devices substitutes carry MSL 1 (Unlimited), eliminating moisture sensitivity constraints. This represents an improvement in handling and storage flexibility.
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