Part A
AD8421BRMZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 2861 Stückzahl
- Package
- TSSOP-8
- Series
- Linear-Verstärker.Instrumentation, OP-Verstärker, Pufferverstärker
Replacement verdict
Compatible functional replacement candidate
The AD8421ARMZ and AD8421BRMZ are functionally interchangeable instrumentation amplifiers sharing identical pinout, package, supply range, and gain configuration, with the B-grade offering tighter gain error and offset voltage specifications. The B-grade is a valid drop-in candidate where enhanced DC precision is required, while the A-grade remains suitable for standard-precision applications.
Package and Pinout
High match
Supply Voltage Range
High match
Gain Configuration
High match
DC Precision Grade
Validation required
Parts at a glance
Part B
AD8421ARMZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 6314 Stückzahl
- Package
- TSSOP-8
- Series
- Linear-Verstärker.Instrumentation, OP-Verstärker, Pufferverstärker
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AD8421ARMZ | AD8421BRMZ | Why it matters |
|---|---|---|---|
| Gain Error (G=1, max) | 0.30% | 0.10% | Lower gain error improves absolute accuracy of the amplified signal, which is critical for precision measurement chains. |
| Input Offset Voltage (max) | 60 µV | 25 µV | Offset voltage directly adds DC error to the measured signal; a lower value enables more accurate low-level signal acquisition. |
| Input Offset Voltage Drift (max) | 0.6 µV/°C | 0.3 µV/°C | Drift determines offset stability over temperature, affecting accuracy in environments with varying thermal conditions. |
| Input Bias Current (max) | 2.0 nA | 1.0 nA | Bias current interacts with source impedance to create error; lower bias current supports higher-impedance sensor interfaces. |
| CMRR (G=1, min) | 80 dB | 86 dB | Common-mode rejection determines how well unwanted common-mode noise is suppressed, impacting measurement integrity. |
| Input Voltage Noise (1 kHz, typ) | 3.2 nV/√Hz | 3.2 nV/√Hz | Voltage noise sets the noise floor for low-level signals; identical values mean equivalent noise performance. |
| Bandwidth (G=1, -3 dB) | 10 MHz | 10 MHz | Bandwidth defines the maximum signal frequency the amplifier can handle with acceptable gain; identical values indicate equivalent AC response. |
| Operating Temperature Range | -40°C to +85°C | -40°C to +85°C | The temperature range defines the environments in which the part can be reliably operated; identical ranges mean equivalent environmental capability. |
| Supply Voltage Range | ±2.5 V to ±18 V | ±2.5 V to ±18 V | Supply range determines compatibility with the system power rails; identical ranges mean the parts are interchangeable in the same supply design. |
| Package | 8-Lead MSOP | 8-Lead MSOP | Package compatibility ensures the parts are drop-in replacements on the same PCB footprint. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD8421BRMZ | AD8421ARMZ |
|---|---|---|
| Part Status | Active | Active |
| Amplifier Type | Instrumentation | Instrumentation |
| Number of Circuits | 1 | 1 |
| Slew Rate | 35V/µs | 35V/µs |
| -3 dB Bandwidth | 10 MHz | 10 MHz |
| Current - Input Bias | 100 pA | 1 nA |
| Voltage - Input Offset | 25 µV | 60 µV |
| Supply Current | 2mA | 2mA |
| Current - Output / Channel | 65 mA | 65 mA |
| Voltage - Supply Span(Min) | 5 V | 5 V |
| Voltage - Supply Span(Max) | 36 V | 36 V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What is the primary difference between the AD8421ARMZ and AD8421BRMZ?
The AD8421ARMZ and AD8421BRMZ are both AD8421 instrumentation amplifiers in an 8-lead MSOP package, but they differ in grade and specified performance. The AD8421BRMZ is the higher-grade version with tighter guaranteed specifications, while the AD8421ARMZ is the standard grade. Both share the same pinout and function.
Are the AD8421ARMZ and AD8421BRMZ pin-compatible and package-compatible?
Yes. Both devices are offered in the same 8-lead MSOP (RM) package with identical pin functions, so they are pin-compatible and share the same PCB land pattern. The difference is in guaranteed electrical specifications, not package or pinout.
How do the gain error specifications compare between the A and B grades?
The B grade (AD8421BRMZ) is specified with tighter gain error than the A grade (AD8421ARMZ). The B grade offers lower maximum gain error over the specified temperature range, making it preferable for applications requiring tighter gain accuracy. Designers should consult the official AD8421 datasheet for the exact gain error limits for each grade.
How does the offset voltage performance differ between the two grades?
The AD8421BRMZ (B grade) is specified with lower maximum input offset voltage and lower offset voltage drift than the AD8421ARMZ (A grade). This makes the B grade better suited for precision DC applications where offset and drift are critical. Exact limits are defined in the AD8421 datasheet.
Do both grades share the same gain-setting resistor and gain equation?
Yes. Both the AD8421ARMZ and AD8421BRMZ use the same external gain-setting resistor connected between the RG pins, and both follow the same gain equation, G = 1 + (9.9 kΩ / RG). The gain-setting method is identical across both grades.
Can the AD8421ARMZ be replaced by the AD8421BRMZ in an existing design?
Because both parts are pin-compatible and share the same package and gain configuration, the AD8421BRMZ can generally be used where the AD8421ARMZ was designed in, and it offers tighter guaranteed specifications. However, the replacement should be validated against the target design requirements and the manufacturer datasheet before production use.
Which grade should be selected for precision measurement applications?
For precision measurement applications requiring tighter gain accuracy, lower offset voltage, and lower drift, the AD8421BRMZ (B grade) is the appropriate choice. The AD8421ARMZ (A grade) is suitable for applications where the standard-grade specifications are sufficient. Selection should be based on the guaranteed limits published in the AD8421 datasheet.