Part A
AD8221ARZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 4567 PCS
- Package
- SOIC-8
- Series
- Linear - Amplifiers - Instrumentation, OP Amps, Buffer Amps
Replacement verdict
Compatible functional replacement candidate
The AD8221ARZ and AD8221BRZ are functionally interchangeable instrumentation amplifiers sharing identical pinout, package, supply range, and gain-setting architecture; the BRZ grade offers tighter gain and offset specifications, making it a valid drop-in candidate where the ARZ grade's accuracy tolerances are acceptable.
Package and Pinout
High match
Supply Voltage Range
High match
Gain Range and Configuration
High match
Gain and Offset Accuracy Grade
Validation required
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AD8221ARZ | AD8221BRZ | Why it matters |
|---|---|---|---|
| Gain Error (G=1, max) | 0.1% | 0.02% | Lower gain error improves absolute accuracy of the amplified signal, which is critical in precision measurement and bridge transducer applications. |
| Input Offset Voltage (max, RTI) | 60 µV | 25 µV | Offset voltage directly adds to the measured signal; a lower offset reduces DC error, especially important for low-level sensor signals. |
| Input Offset Voltage Drift (max) | 0.8 µV/°C | 0.3 µV/°C | Drift determines offset stability over temperature; lower drift maintains accuracy across the operating temperature range without recalibration. |
| Input Bias Current (max, 25°C) | 1.5 nA | 1.0 nA | Bias current flowing through source impedance creates error voltage; lower bias current benefits high-impedance sensor interfaces. |
| CMRR (G=1, min, DC to 60 Hz) | 80 dB | 90 dB | Common-mode rejection suppresses unwanted common-mode noise; higher CMRR improves signal fidelity in noisy industrial environments. |
| Noise (RTI, 1 kHz, max) | 10 nV/√Hz | 8 nV/√Hz | Lower input-referred noise improves resolution for small signals and determines the minimum detectable signal level. |
| Gain Nonlinearity (G=1 to 1000, max) | 10 ppm | 5 ppm | Nonlinearity affects accuracy at higher gains; lower nonlinearity ensures consistent gain accuracy across the signal range. |
| Supply Voltage Range | ±2.3 V to ±18 V | ±2.3 V to ±18 V | Wide supply range allows operation from battery-powered to industrial supply rails; identical range means no change in power design. |
| Gain Range (pin-programmable) | 1 to 1000 | 1 to 1000 | Pin-programmable gain via a single resistor provides design flexibility; identical range ensures the same external resistor network works. |
| Package | 8-Lead SOIC | 8-Lead SOIC | Identical package and pinout allow drop-in replacement on the same PCB footprint without layout changes. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD8221ARZ | AD8221BRZ |
|---|---|---|
| Part Status | Active | Active |
| Amplifier Type | Instrumentation | Instrumentation |
| Number of Circuits | 1 | 1 |
| Slew Rate | 2V/µs | 2V/µs |
| -3 dB Bandwidth | 825 kHz | 825 kHz |
| Current - Input Bias | 500 pA | 200 pA |
| Voltage - Input Offset | 60 µV | 25 µV |
| Supply Current | 900µA | 900µA |
| Current - Output / Channel | 18 mA | 18 mA |
| Voltage - Supply Span(Min) | 4.6 V | 4.6 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 are the main differences between the AD8221ARZ and AD8221BRZ?
Both are AD8221 instrumentation amplifiers in the same 8-lead SOIC package, but they differ in grade and specified performance. The AD8221BRZ is the higher-grade version with tighter guaranteed specifications, including lower offset voltage, lower offset drift, lower gain error, and higher CMRR than the AD8221ARZ. The BRZ grade is specified over the same temperature range but with tighter limits on key DC and AC parameters.
Are the AD8221ARZ and AD8221BRZ pin-compatible and package-compatible?
Yes. Both devices are offered in the same 8-lead SOIC (R-8) package with identical pin functions, so they are pin-compatible and can use the same PCB land pattern. Electrical grade differences, not package differences, are the distinguishing factor.
Can the AD8221ARZ be replaced directly by the AD8221BRZ in an existing design?
In most cases yes, because the pinout and package are identical and the BRZ grade meets or exceeds the ARZ grade specifications. However, the replacement should be validated against the design's error budget, since the BRZ grade has tighter guaranteed limits and the circuit's performance may change (typically improve) within those limits.
Which grade offers better offset voltage and offset drift performance?
The AD8221BRZ offers better guaranteed offset performance. The BRZ grade has a lower maximum input offset voltage and lower maximum input offset voltage drift over temperature compared with the AD8221ARZ, making it preferable for precision DC applications where offset error must be tightly controlled.
Do both grades share the same gain range and gain-setting method?
Yes. Both the AD8221ARZ and AD8221BRZ use the same single external resistor to set gain, with the same gain equation and the same specified gain range. The difference is that the BRZ grade guarantees tighter gain error and lower gain drift limits than the ARZ grade.
Is the CMRR specification different between the AD8221ARZ and AD8221BRZ?
Yes. The AD8221BRZ guarantees a higher minimum common-mode rejection ratio than the AD8221ARZ, particularly at higher gains. For applications requiring maximum rejection of common-mode noise, the BRZ grade provides the tighter guaranteed CMRR limit.
Do the AD8221ARZ and AD8221BRZ have the same supply voltage and operating temperature range?
Yes. Both grades operate from the same supply voltage range and are specified over the same industrial temperature range. The grade difference is in guaranteed parametric limits, not in supply requirements or temperature range.
Which grade should be selected for a cost-sensitive versus a precision application?
The AD8221ARZ is typically the more economical choice for applications where the looser guaranteed limits still meet the error budget. The AD8221BRZ is intended for precision applications that require tighter offset, drift, gain error, and CMRR specifications. Selection should be based on the design's error budget and the guaranteed limits published in the respective datasheet grade tables.