Part A
AD8221ARM
Công ty Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 2853 PCS
- Package
- TSSOP-8
- Series
- Linear - Amplifiers - Instrumentation, OP Amps, Buffer Amps
Replacement verdict
Compatible functional replacement candidate
The AD8220ARMZ and AD8221ARM are both precision instrumentation amplifiers in the same 8-lead MSOP package with identical pinout, making them strong functional replacement candidates. However, the AD8221ARM offers higher gain accuracy and wider bandwidth while the AD8220ARMZ provides JFET input with lower input bias current, so the substitution should be validated against the specific input source impedance and bandwidth requirements of the target design.
Package Type
High match
Pin Configuration
High match
Input Bias Current
Validation required
Gain Bandwidth
Validation required
Parts at a glance
Part B
AD8220ARMZ
Công ty Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 4214 PCS
- Package
- TSSOP-8
- Series
- Linear - Amplifiers - Instrumentation, OP Amps, Buffer Amps
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AD8220ARMZ | AD8221ARM | Why it matters |
|---|---|---|---|
| Amplifier Type | Instrumentation Amplifier with JFET Input | Instrumentation Amplifier with Bipolar Input | Input stage topology determines input bias current, noise, and input impedance, directly affecting sensor interfacing suitability. |
| Input Bias Current (typ) | 10 pA | 0.5 nA | Lower bias current reduces errors in high-impedance sensor applications such as photodiode and pH probes. |
| Input Offset Voltage (max) | 250 µV | 60 µV | Offset voltage directly adds DC error to the amplified signal; lower offset improves precision in low-level signal measurement. |
| Input Voltage Noise (1 kHz, typ) | 14 nV/√Hz | 8 nV/√Hz | Lower voltage noise improves signal-to-noise ratio for small-signal amplification. |
| Gain Bandwidth Product | 1 MHz | 825 kHz | Bandwidth limits the maximum frequency of signals that can be amplified at a given gain. |
| Supply Voltage Range | ±2.25 V to ±18 V (4.5 V to 36 V) | ±2.3 V to ±18 V (4.6 V to 36 V) | Supply range determines compatibility with the system power rails and headroom for signal swing. |
| CMRR (G=100, typ) | 100 dB | 120 dB | Higher common-mode rejection improves accuracy in the presence of large common-mode interference. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +125 °C | Temperature range affects suitability for industrial and automotive environments. |
| Package | 8-Lead MSOP | 8-Lead MSOP | Package compatibility enables drop-in replacement on the same PCB footprint. |
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 | AD8221ARM | AD8220ARMZ |
|---|---|---|
| Part Status | Obsolete | Active |
| Amplifier Type | Instrumentation | Instrumentation |
| Number of Circuits | 1 | 1 |
| Slew Rate | 2V/µs | 2V/µs |
| -3 dB Bandwidth | 825 kHz | 1.5 MHz |
| Current - Input Bias | 500 pA | 25 pA |
| Voltage - Input Offset | 60 µV | 250 µV |
| Supply Current | 900µA | 750µA |
| Current - Output / Channel | 18 mA | 15 mA |
| Voltage - Supply Span(Min) | 4.6 V | 4.5 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 |
| Output Type | - | Rail-to-Rail |
Frequently asked questions
What are the primary functional differences between the AD8220ARMZ and the AD8221ARM?
The AD8220ARMZ is a JFET-input instrumentation amplifier optimized for high input impedance and low input bias current, making it suitable for high-impedance sensor interfaces. The AD8221ARM is a bipolar-input instrumentation amplifier designed for high common-mode rejection ratio (CMRR) and low voltage noise, making it better suited for precision bridge and low-impedance transducer applications. They are not pin-compatible substitutes in all designs because their input architectures and key specifications differ.
Are the AD8220ARMZ and AD8221ARM pin-compatible?
Both devices are offered in an 8-lead MSOP (RM) package, and their pinouts follow the standard instrumentation amplifier configuration (gain-setting resistor pins, input pins, supply pins, output, and reference). However, because the internal architectures differ, designers must verify that the surrounding circuit, gain resistor selection, and supply decoupling are appropriate for each device before treating them as drop-in replacements.
How do the input bias currents of the AD8220ARMZ and AD8221ARM compare?
The AD8220ARMZ, with its JFET input stage, provides very low input bias current (typically in the picoampere range), which minimizes errors in high-impedance source applications. The AD8221ARM uses a bipolar input stage and has higher input bias current (typically in the nanoampere range). For circuits with high source impedance, the AD8220ARMZ generally offers an advantage in bias-current-induced offset.
Which device offers better common-mode rejection for bridge sensor applications?
The AD8221ARM is specifically designed for high CMRR performance and is commonly used in precision bridge and strain-gauge applications where excellent common-mode rejection is critical. The AD8220ARMZ also provides good CMRR but is optimized more for high input impedance and low bias current. For bridge sensors with low source impedance, the AD8221ARM is typically the preferred choice.
Can the AD8220ARMZ and AD8221ARM operate from the same supply voltages?
Both devices support dual-supply operation over a wide range and are specified for operation on supplies such as ±5 V to ±15 V, as well as single-supply configurations within their specified limits. Designers should consult the respective manufacturer datasheets to confirm the exact supply range and output swing requirements for each device in the target circuit.
How do the gain-setting configurations of the AD8220ARMZ and AD8221ARM differ?
Both devices use an external gain-setting resistor connected between the RG pins to program gain, following the standard instrumentation amplifier gain equation. The specific gain equation and recommended resistor values differ between the two devices, so the gain resistor must be recalculated when substituting one for the other. Designers should refer to each device's datasheet for the exact gain formula.
Which device is better suited for high-impedance sensor interfaces?
The AD8220ARMZ is generally better suited for high-impedance sensor interfaces because its JFET input stage provides very low input bias current and high input impedance, reducing loading effects and offset errors. The AD8221ARM, with its bipolar input stage, is better suited for low-impedance, precision applications where low noise and high CMRR are the dominant requirements.