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INA121UG4 Instrumentation Amplifier Equivalent & Substitute Parts
Part Overview
The INA121UG4 is a single-circuit instrumentation amplifier manufactured by Texas Instruments in 8-SOIC surface mount packaging. This device is classified as obsolete product status. The INA121UG4 operates across a wide supply voltage range of 4.5 V to 36 V and is designed for precision signal conditioning applications requiring low input bias current and low input offset voltage. Due to its obsolete status, equivalent and substitute parts from active product lines are necessary for new designs and ongoing production requirements.
Substiute Parts
Key Parameters
| Parameter | Value | Unit |
|---|---|---|
| Amplifier Type | Instrumentation | — |
| Number of Circuits | 1 | — |
| Package / Case | 8-SOIC (0.154", 3.90mm Width) | — |
| Mounting Type | Surface Mount | — |
| Slew Rate | 0.7 | V/µs |
| -3dB Bandwidth | 5 | kHz |
| Current - Input Bias | 4 | pA |
| Voltage - Input Offset | 200 | µV |
| Current - Supply | 450 | µA |
| Current - Output / Channel | 14 | mA |
| Voltage - Supply Span (Min) | 4.5 | V |
| Voltage - Supply Span (Max) | 36 | V |
| Operating Temperature | -40°C to 85°C | — |
| RoHS Status | ROHS3 Compliant | — |
| Moisture Sensitivity Level (MSL) | 3 (168 Hours) | — |
Substitute Part Grouping Explanation
Substitution of the INA121UG4 is determined by strict equivalence in the following critical parameters: amplifier type (instrumentation), number of circuits (1), package type (8-SOIC surface mount), and operating temperature range (-40°C to 85°C). All substitute parts must maintain identical mechanical compatibility and electrical interface characteristics.
The substitute parts are grouped into two categories based on electrical performance characteristics:
Category 1: Texas Instruments INA121 Series (Direct Functional Equivalent) The INA121U maintains identical electrical specifications to the INA121UG4, including slew rate (0.7 V/µs), bandwidth (5 kHz), input bias current (4 pA), input offset voltage (200 µV), and supply current (450 µA). This part differs only in product status (active versus obsolete) and packaging format (tube versus unspecified).
Category 2: Analog Devices AD620 and AD622 Series (Enhanced Performance Alternatives) The AD620 and AD622 families provide superior electrical performance compared to the INA121UG4 while maintaining identical package and mounting specifications. These parts feature increased slew rate (1.2 V/µs), expanded bandwidth (1 MHz), and lower input offset voltage. The AD622 series additionally provides significantly lower input bias current (2 nA versus 4 pA or 500 pA). All AD620 and AD622 variants are active products with MSL rating of 1 (unlimited moisture sensitivity).
Substitution is valid when the application requirements permit the enhanced performance characteristics of the AD620 and AD622 families, or when direct functional equivalence is required, in which case the INA121U is the appropriate selection.
Parameter Comparison
| Parameter | INA121UG4 | INA121U | AD620ARZ | AD620BRZ | AD622ARZ |
|---|---|---|---|---|---|
| Manufacturer | Texas Instruments | Texas Instruments | Analog Devices Inc. | Analog Devices Inc. | Analog Devices Inc. |
| Product Status | Obsolete | Active | Active | Active | Active |
| Package / Case | 8-SOIC (0.154", 3.90mm Width) | 8-SOIC (0.154", 3.90mm Width) | 8-SOIC (0.154", 3.90mm Width) | 8-SOIC (0.154", 3.90mm Width) | 8-SOIC (0.154", 3.90mm Width) |
| Mounting Type | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount |
| Slew Rate (V/µs) | 0.7 | 0.7 | 1.2 | 1.2 | 1.2 |
| -3dB Bandwidth (kHz) | 5 | 5 | 1000 | 1000 | 1000 |
| Current - Input Bias (pA) | 4 | 4 | 500 | 500 | 2000 |
| Voltage - Input Offset (µV) | 200 | 200 | 30 | 15 | 60 |
| Current - Supply (µA) | 450 | 450 | 900 | 900 | 900 |
| Current - Output / Channel (mA) | 14 | 14 | 18 | 18 | 18 |
| Voltage - Supply Span (Min) | 4.5 V | 4.5 V | 4.6 V | 4.6 V | 5.2 V |
| Voltage - Supply Span (Max) | 36 V | 36 V | 36 V | 36 V | 36 V |
| Operating Temperature | -40°C to 85°C | -40°C to 85°C | -40°C to 85°C | -40°C to 85°C | -40°C to 85°C |
| MSL Rating | 3 (168 Hours) | 3 (168 Hours) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) |
| RoHS Status | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant |
Engineering Selection Recommendations
For Direct Functional Replacement: The INA121U is the appropriate selection when exact electrical performance matching is required. This part maintains identical specifications across all measured parameters including slew rate, bandwidth, input bias current, and input offset voltage. The INA121U is an active product, eliminating obsolescence risk while preserving the electrical characteristics of the original INA121UG4 design.
For Enhanced Performance Applications: The AD620 series (AD620ARZ, AD620BRZ, and their reel variants) provides superior performance characteristics suitable for applications requiring higher bandwidth (1 MHz versus 5 kHz), faster slew rate (1.2 V/µs versus 0.7 V/µs), and lower input offset voltage (15 µV to 30 µV versus 200 µV). The AD620BRZ variants offer the lowest input offset voltage (15 µV) within this family. These parts are active products with MSL rating of 1, indicating superior moisture resistance compared to the INA121 series.
For Ultra-Low Input Bias Current Applications: The AD622 series (AD622ARZ and reel variants) provides the lowest input bias current specification (2 nA) among all substitute options, making this family suitable for high-impedance signal sources. The AD622 requires a minimum supply voltage of 5.2 V compared to 4.5 V for other options. All AD622 variants are active products with MSL rating of 1.
Compliance and Certification: All substitute parts maintain ROHS3 compliance and REACH unaffected status, matching the regulatory profile of the original INA121UG4. Packaging options include tube and cut tape with digi-reel formats to accommodate different procurement and assembly workflows.
Frequently Asked Questions (FAQ)
Q: Can the INA121U directly replace the INA121UG4 in existing designs?
A: Yes. The INA121U maintains identical electrical specifications and operates within the same temperature range (-40°C to 85°C). Both parts use 8-SOIC surface mount packaging with identical pinout and mechanical dimensions. The primary difference is product status (active versus obsolete) and packaging format. No circuit modifications are required.
Q: What are the key differences between the INA121U and AD620 series?
A: The INA121U and AD620 series differ in bandwidth, slew rate, and input offset voltage. The AD620 provides 1 MHz bandwidth compared to 5 kHz for the INA121U, and 1.2 V/µs slew rate compared to 0.7 V/µs. Input offset voltage is significantly lower in the AD620 (15 µV to 30 µV versus 200 µV). Input bias current is higher in the AD620 (500 pA versus 4 pA). Supply current is doubled in the AD620 (900 µA versus 450 µA). All parts share identical 8-SOIC packaging and -40°C to 85°C operating temperature range.
Q: When should I select the AD622 instead of the AD620?
A: Select the AD622 when applications require ultra-low input bias current (2 nA). The AD622 is suitable for high-impedance signal sources where input bias current must be minimized. The AD622 requires a minimum supply voltage of 5.2 V, compared to 4.5 V for the INA121U and 4.6 V for the AD620. All other performance characteristics (slew rate, bandwidth, output current) are identical between AD620 and AD622 families.
Q: Are there packaging format differences among the substitute parts?
A: Yes. The INA121U is available in tube packaging. The AD620 and AD622 families are available in multiple formats: tube packaging (AD620ARZ, AD620BRZ, AD622ARZ) and cut tape with digi-reel packaging (AD620ARZ-REEL, AD620ARZ-REEL7, AD620BRZ-R7, AD620BRZ-RL, AD622ARZ-R7, AD622ARZ-RL). All variants maintain identical electrical specifications and 8-SOIC package dimensions. Selection between formats depends on procurement and assembly requirements.
Q: What is the significance of the MSL rating difference?
A: The INA121U has MSL rating of 3 (168 hours), while AD620 and AD622 families have MSL rating of 1 (unlimited). MSL rating indicates moisture sensitivity during storage and handling. Lower MSL ratings (1 versus 3) provide greater tolerance to humidity exposure and longer shelf life without requiring special moisture-controlled storage conditions. For applications with extended storage periods or humid environments, the AD620 and AD622 families offer superior reliability.
Q: Can I use AD620 or AD622 in applications originally designed for INA121UG4?
A: Substitution is valid when the application requirements permit the enhanced performance characteristics. The higher bandwidth (1 MHz), faster slew rate (1.2 V/µs), and lower input offset voltage of the AD620 and AD622 families are compatible with applications designed for the INA121UG4. However, the increased supply current (900 µA versus 450 µA) and higher input bias current (500 pA or 2 nA versus 4 pA) must be evaluated against specific circuit requirements. Mechanical compatibility is guaranteed due to identical 8-SOIC packaging.
Q: Are all substitute parts RoHS3 compliant?
A: Yes. The INA121U, AD620 series, and AD622 series are all ROHS3 compliant and REACH unaffected, matching the regulatory status of the original INA121UG4. All parts are suitable for applications requiring RoHS compliance.
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