INA128UG4 Equivalent & Substitute Parts

Part Overview

The INA128UG4 is an instrumentation amplifier manufactured by Texas Instruments, housed in an 8-SOIC surface mount package. This device is classified as obsolete, though 995 units remain in stock. The INA128UG4 serves applications requiring single-circuit instrumentation amplification with low input bias current and low input offset voltage across industrial temperature ranges. Due to its obsolete status, equivalent and substitute parts from active product lines are necessary for new designs and long-term supply chain continuity.

Key Parameters

Parameter	Value	Unit
Amplifier Type	Instrumentation	—
Number of Circuits	1	—
Slew Rate	4	V/µs
-3dB Bandwidth	1.3	MHz
Current - Input Bias	2	nA
Voltage - Input Offset	10	µV
Current - Supply	700	µA
Current - Output / Channel	15	mA
Voltage - Supply Span (Min)	4.5	V
Voltage - Supply Span (Max)	36	V
Operating Temperature	-40 to 85	°C
Package / Case	8-SOIC (0.154", 3.90mm Width)	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level	3 (168 Hours)	—

Substitute Part Grouping Explanation

Substitution of the INA128UG4 is determined by strict equivalence across the following critical parameters:

Primary Substitution Criteria:

Amplifier Type: Instrumentation
Number of Circuits: 1
Package / Case: 8-SOIC (0.154", 3.90mm Width)
Mounting Type: Surface Mount
Operating Temperature Range: -40°C to 85°C
Supply Voltage Range: Minimum 4.5 V, Maximum 36 V

Secondary Performance Parameters:

Slew Rate: 4 V/µs (INA128UG4 baseline)
-3dB Bandwidth: 1.3 MHz (INA128UG4 baseline)
Input Bias Current: 2 nA (INA128UG4 baseline)
Input Offset Voltage: 10 µV (INA128UG4 baseline)

The INA128U from Texas Instruments provides direct equivalence with identical electrical specifications and active product status. Analog Devices AD620 and AD621 series parts offer functional substitution within the same package and temperature range, though with different performance characteristics in slew rate, bandwidth, input bias current, and input offset voltage. These differences must be evaluated against specific application requirements.

Parameter Comparison

Parameter	INA128UG4	INA128U	AD620ARZ	AD620BRZ	AD621ARZ
Manufacturer	Texas Instruments	Texas Instruments	Analog Devices Inc.	Analog Devices Inc.	Analog Devices Inc.
Product Status	Obsolete	Active	Active	Active	Active
Slew Rate (V/µs)	4	4	1.2	1.2	1.2
-3dB Bandwidth (MHz)	1.3	1.3	1	1	0.8
Current - Input Bias (nA)	2	2	0.5	0.5	0.5
Voltage - Input Offset (µV)	10	10	30	15	75
Current - Supply (µA)	700	700	900	900	900
Current - Output / Channel (mA)	15	15	18	18	18
Voltage - Supply Span (Min) (V)	4.5	4.5	4.6	4.6	4.6
Voltage - Supply Span (Max) (V)	36	36	36	36	36
Operating Temperature (°C)	-40 to 85	-40 to 85	-40 to 85	-40 to 85	-40 to 85
Package / Case	8-SOIC	8-SOIC	8-SOIC	8-SOIC	8-SOIC
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level	3 (168 Hours)	3 (168 Hours)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

Primary Recommendation: INA128U

The INA128U from Texas Instruments is the direct equivalent to the INA128UG4. It maintains identical electrical specifications including 4 V/µs slew rate, 1.3 MHz bandwidth, 2 nA input bias current, and 10 µV input offset voltage. The INA128U is classified as an active product with significantly higher inventory availability (83,580 units). Both parts share ROHS3 compliance and identical supply voltage ranges. The primary difference is packaging format (Tube for INA128U versus the original part's specification). This substitution requires no circuit redesign and provides full functional compatibility.

Secondary Recommendation: AD620 Series (Analog Devices Inc.)

The AD620ARZ, AD620BRZ, and their packaging variants (AD620ARZ-REEL, AD620ARZ-REEL7, AD620BRZ-R7, AD620BRZ-RL) provide functional substitution within the same 8-SOIC package and operating temperature range. These parts feature lower input bias current (0.5 nA versus 2 nA) and improved moisture sensitivity (MSL 1 Unlimited versus MSL 3). However, they exhibit reduced slew rate (1.2 V/µs versus 4 V/µs) and lower bandwidth (1 MHz versus 1.3 MHz). The AD620BRZ variants offer superior input offset voltage performance (15 µV versus 10 µV for INA128UG4). Selection of AD620 series requires evaluation of application bandwidth and slew rate requirements.

Tertiary Recommendation: AD621 Series (Analog Devices Inc.)

The AD621ARZ, AD621ARZ-R7, and AD621ARZ-RL provide functional substitution with the same package and temperature range. These parts feature the lowest input bias current (0.5 nA) and improved moisture sensitivity (MSL 1). However, they exhibit the lowest bandwidth (800 kHz) and highest input offset voltage (75 µV) among the substitute options. The AD621 series is suitable only for applications where bandwidth below 800 kHz is acceptable and input offset voltage of 75 µV does not exceed circuit requirements.

Compliance and Certification:

All recommended substitutes maintain ROHS3 compliance and REACH Unaffected status, matching the original INA128UG4 specifications. All parts are classified under HTSUS 8542.33.0001 and ECCN EAR99.

Frequently Asked Questions (FAQ)

Q: Can the INA128U directly replace the INA128UG4 in existing designs?

A: Yes. The INA128U provides direct electrical equivalence with identical slew rate (4 V/µs), bandwidth (1.3 MHz), input bias current (2 nA), and input offset voltage (10 µV). Both parts operate across -40°C to 85°C and support 4.5 V to 36 V supply ranges. The primary difference is packaging format. No circuit modifications are required.

Q: What are the key performance differences between INA128U and AD620 series?

A: The INA128U maintains 4 V/µs slew rate and 1.3 MHz bandwidth. The AD620 series operates at 1.2 V/µs slew rate and 1 MHz bandwidth. The AD620 series provides superior input bias current (0.5 nA versus 2 nA) and improved moisture sensitivity (MSL 1 versus MSL 3). Applications requiring high-speed signal conditioning or bandwidth above 1 MHz should retain the INA128U or equivalent. Applications prioritizing low input bias current and moisture resistance may benefit from AD620 series substitution.

Q: Are all substitute parts available in the same 8-SOIC package?

A: Yes. All recommended substitutes are housed in 8-SOIC (0.154", 3.90mm Width) surface mount packages. Packaging format variants (Tube, Cut Tape & Digi-Reel, Tape & Reel) differ among substitute options but do not affect electrical performance or PCB footprint compatibility.

Q: What is the significance of Moisture Sensitivity Level differences?

A: The INA128UG4 carries MSL 3 (168 Hours), requiring controlled storage and handling. The AD620 and AD621 series carry MSL 1 (Unlimited), eliminating moisture sensitivity constraints. For applications with extended storage periods or high-humidity environments, AD620 or AD621 series substitution reduces handling and storage requirements.

Q: Which substitute is appropriate for low-frequency applications below 800 kHz?

A: The AD621 series (AD621ARZ, AD621ARZ-R7, AD621ARZ-RL) operates at 800 kHz bandwidth and is suitable for applications where signal frequencies remain below this limit. However, the AD621 series exhibits the highest input offset voltage (75 µV) among all options. Verify that 75 µV input offset voltage is acceptable for the specific application before selecting AD621 series.

Q: Do all substitutes maintain the same supply voltage range?

A: The INA128U maintains the original 4.5 V to 36 V range. The AD620 and AD621 series operate at 4.6 V minimum to 36 V maximum. Applications operating at exactly 4.5 V supply voltage require the INA128U. Applications at 4.6 V or higher support all substitute options.

Q: What packaging options are available for high-volume production?

A: For high-volume applications, Cut Tape & Digi-Reel packaging (AD620ARZ-REEL, AD620ARZ-REEL7, AD620BRZ-R7, AD621ARZ-R7) and Tape & Reel options (AD621ARZ-RL, AD620BRZ-RL) provide automated assembly compatibility. The INA128U is available in Tube packaging. Verify packaging compatibility with assembly equipment before final selection.

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