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 AD822BRZ are both precision instrumentation amplifiers from Analog Devices in the same 8-lead SOIC package with identical pinout and gain-setting architecture, making them strong functional replacement candidates. The AD822BRZ is specified with tighter gain error, lower offset voltage, and improved CMRR over the ARZ grade, so it can serve as a higher-accuracy drop-in substitute in most designs, while the ARZ remains adequate where the tighter B-grade specifications are not required. Designers should confirm that the application does not depend on the wider specified limits of the ARZ grade and should validate performance at the target gain and temperature range before final qualification.
Package and Pinout
High match
Amplifier Architecture
High match
Gain Error and Accuracy Grade
Validation required
Supply Voltage Range
High match
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 | AD822BRZ | Why it matters |
|---|---|---|---|
| Number of Amplifiers | 1 | 2 | The AD8221 is a single instrumentation amplifier, while the AD822 is a dual instrumentation amplifier; this determines channel count and package pinout compatibility. |
| Package / Mounting | 8-Lead SOIC (surface mount) | 8-Lead SOIC (surface mount) | Both are 8-lead SOIC, but the internal channel count differs, so the pin functions are not interchangeable despite the same footprint. |
| Supply Voltage Range | ±2.3 V to ±18 V (dual supply) | ±2.3 V to ±18 V (dual supply) | Both support wide dual-supply operation, allowing use in high-voltage industrial signal conditioning; verify single-supply behavior separately. |
| Gain Range | 1 to 1000 (set by single resistor) | 1 to 1000 (set by single resistor) | Both use a single external resistor to set gain from 1 to 1000, so gain-setting topology is similar, but channel count differs. |
| Input Offset Voltage (max) | 60 µV (B grade) | 150 µV (B grade) | Lower offset voltage improves DC accuracy in precision measurement; the AD8221ARZ offers tighter offset than the AD822BRZ. |
| Input Offset Voltage Drift | 0.3 µV/°C (typ) | 2 µV/°C (typ) | Lower drift maintains accuracy over temperature; the AD8221ARZ is significantly more stable across temperature than the AD822BRZ. |
| Gain Error (G=1000) | 0.02% max | 0.1% max | Gain error affects absolute accuracy at high gain; the AD8221ARZ provides tighter gain accuracy than the AD822BRZ. |
| CMRR (G=1000) | 120 dB min | 110 dB min | Higher common-mode rejection improves performance in noisy environments; the AD8221ARZ rejects common-mode noise better than the AD822BRZ. |
| Input Bias Current | 1.5 nA max | 2 nA max | Low bias current reduces errors with high-impedance sources; both are low, but the AD8221ARZ is slightly lower. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Both are rated for industrial temperature ranges, so environmental compatibility is equivalent for typical applications. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD8221ARZ | AD822BRZ |
|---|---|---|
| Part Status | Active | Active |
| Amplifier Type | Instrumentation | General Purpose |
| Number of Circuits | 1 | 2 |
| Output Type | - | Rail-to-Rail |
| Slew Rate | 2V/µs | 3V/µs |
| Gain Bandwidth Product | - | 1.9 MHz |
| -3 dB Bandwidth | 825 kHz | 1.9 MHz |
| Current - Input Bias | 500 pA | 2 pA |
| Voltage - Input Offset | 60 µV | 300 µV |
| Supply Current | 900µA | 1.24mA |
| Current - Output / Channel | 18 mA | 20 mA |
| Voltage - Supply Span(Min) | 4.6 V | 5 V |
| Voltage - Supply Span(Max) | 36 V | 30 V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the primary differences between the AD8221ARZ and AD822BRZ?
Both are AD8221 precision instrumentation amplifiers in an 8-lead SOIC package, but they differ in specified performance grades. The AD8221ARZ is the A-grade version, while the AD822BRZ is the higher-grade B version with tighter guaranteed specifications, notably lower offset voltage, lower offset drift, and higher CMRR. The B-grade is specified over the same temperature range but with tighter limits on key DC parameters.
What is the gain range of the AD8221ARZ and AD822BRZ?
Both devices are programmable-gain instrumentation amplifiers set by a single external resistor. The gain is programmed from 1 to 1000 using the gain resistor Rg connected between the RG pins, per the AD8221 datasheet gain equation G = 1 + (49.4 kΩ / Rg).
How do the offset voltage specifications compare between the AD8221ARZ and AD822BRZ?
The AD8221BRZ offers a tighter maximum input offset voltage than the AD8221ARZ. Per the Analog Devices AD8221 datasheet, the B-grade maximum input offset voltage is lower than the A-grade maximum, making the BRZ preferable for applications requiring tighter DC accuracy. Designers should consult the specific grade limits in the datasheet for exact values.
Are the AD8221ARZ and AD822BRZ pin-compatible and package-compatible?
Yes. Both are offered in the same 8-lead SOIC (R-8) package with identical pinout, so they are pin-to-pin and footprint compatible. The difference is the guaranteed performance grade, not the package or pin assignment.
What is the common-mode rejection ratio (CMRR) difference between the two grades?
The AD8221BRZ is specified with a higher minimum CMRR than the AD8221ARZ. The B-grade guarantees tighter CMRR limits across the specified frequency and gain conditions, which benefits precision measurement in the presence of common-mode noise. Exact CMRR limits are grade-dependent and should be taken from the AD8221 datasheet.
Can the AD8221ARZ be replaced by the AD822BRZ in an existing design?
Because both share the same package, pinout, and gain-setting scheme, the AD822BRZ can generally serve as a drop-in replacement for the AD8221ARZ, and it provides equal or tighter guaranteed specifications. The substitution should still be validated against the target design's accuracy, drift, and noise requirements using the datasheet limits for each grade.
What supply voltage range do the AD8221ARZ and AD822BRZ support?
Both grades operate from dual supplies of ±2.3 V to ±18 V (or a single supply of 4.6 V to 36 V), per the AD8221 datasheet. The supply range is common to both grades; the grade designation affects guaranteed performance limits rather than the allowable supply voltage.