Part A
AD8221ARM
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 2853 PCS
- Package
- TSSOP-8
- Series
- Amplificateurs linéaires - instruments, amplificateurs opérationnels, amplificateurs tampons
Replacement verdict
Compatible functional replacement candidate
The AD8220BRMZ and AD8221ARM are both precision instrumentation amplifiers in the same 8-lead MSOP package with comparable supply and temperature ranges, making the AD8221ARM a viable functional replacement candidate for the AD8220BRMZ in many designs. However, the two devices differ in input architecture and bandwidth, so gain-setting, input bias current, and AC performance must be validated against the target application before substitution.
Input Architecture
Validation required
Package Type
High match
Supply Voltage Range
High match
Bandwidth and Gain Range
Validation required
Parts at a glance
Part B
AD8220BRMZ
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 5173 PCS
- Package
- TSSOP-8
- Series
- Amplificateurs linéaires - instruments, amplificateurs opérationnels, amplificateurs tampons
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AD8220BRMZ | AD8221ARM | Why it matters |
|---|---|---|---|
| Amplifier Type | Instrumentation Amplifier with JFET Input | Instrumentation Amplifier with Bipolar Input | Input stage topology determines input bias current, input impedance, and noise characteristics, directly affecting suitability for high-impedance or low-noise sensor interfaces. |
| Input Bias Current (typ) | 10 pA | 0.5 nA | Lower bias current reduces offset errors in high-source-impedance applications such as pH or photodiode sensors; the JFET input of the AD8220 is significantly better here. |
| Input Voltage Noise (1 kHz, typ) | 14 nV/√Hz | 8 nV/√Hz | Lower voltage noise improves signal-to-noise ratio for low-level signals; the AD8221 offers better noise performance for low-impedance sources. |
| Gain Bandwidth Product (G=1) | 1.5 MHz | 825 kHz | Bandwidth determines the maximum signal frequency the amplifier can handle at a given gain; the AD8220 supports higher-frequency signals. |
| Input Offset Voltage (max) | 250 µV | 50 µV | Lower offset voltage reduces DC error at the output; the AD8221 provides tighter DC precision for precision measurement applications. |
| CMRR (G=100, min) | 100 dB | 110 dB | Common-mode rejection ratio determines how well the amplifier rejects common-mode noise; higher CMRR in the AD8221 improves performance in noisy environments. |
| 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 affects compatibility with system power rails; both are similar, but slight differences may matter at the low end of the range. |
| Quiescent Supply Current (typ) | 750 µA | 1 mA | Lower quiescent current reduces power consumption, which is important for battery-powered or low-power instrumentation designs. |
| Package | 8-Lead MSOP | 8-Lead MSOP | Package compatibility ensures the parts are physically interchangeable on the same PCB footprint. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Temperature range confirms both parts are suitable for industrial-grade environments with identical thermal limits. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD8221ARM | AD8220BRMZ |
|---|---|---|
| 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 | 10 pA |
| Voltage - Input Offset | 60 µV | 125 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 AD8220BRMZ and the AD8221ARM?
The AD8220BRMZ is a JFET-input instrumentation amplifier optimized for high input impedance and low input bias current, making it suitable for high-source-impedance sensors. The AD8221ARM is a precision bipolar-input instrumentation amplifier designed for very low offset voltage, low offset drift, and high CMRR in low-frequency precision applications. They differ in input stage topology, input bias current, and offset performance characteristics.
Are the AD8220BRMZ and AD8221ARM pin-compatible in their respective packages?
No. The AD8220BRMZ is supplied in an 8-lead MSOP (RM-8) package, while the AD8221ARM is supplied in an 8-lead MSOP (RM-8) package as well, but the internal pin functions and external component requirements differ between the two devices. Designers must verify the pinout and gain-setting configuration against the respective datasheets before considering any layout reuse.
How do the input bias currents of the AD8220BRMZ and AD8221ARM compare?
The AD8220BRMZ, with its JFET input stage, specifies input bias current in the picoampere range (typically a few pA at room temperature), which is significantly lower than the AD8221ARM's bipolar input bias current, which is specified in the nanoampere range (typically up to approximately 1.5 nA maximum at 25°C). This makes the AD8220BRMZ preferable for high-impedance source applications.
Which device offers better offset voltage and offset drift performance?
The AD8221ARM offers superior DC precision, with a maximum input offset voltage of 25 µV and offset voltage drift of 0.3 µV/°C (B grade). The AD8220BRMZ specifies a maximum input offset voltage of 250 µV (B grade) with correspondingly higher drift. For precision low-frequency DC applications, the AD8221ARM is the stronger choice.
How do the gain-setting methods differ between the AD8220BRMZ and AD8221ARM?
Both devices set gain using a single external resistor (RG) connected across the RG pins, following the standard instrumentation amplifier gain equation G = 1 + (49.4 kΩ / RG). The gain range and resistor value calculations are similar, but designers should confirm the exact RG pin locations and recommended resistor values from each device's respective datasheet.
Which device is better suited for high-source-impedance sensor interfaces?
The AD8220BRMZ is generally better suited for high-source-impedance sensors because its JFET input stage provides very low input bias current (picoampere range), minimizing voltage errors across high source impedances. The AD8221ARM's higher bipolar input bias current can produce larger offset errors when driven from high-impedance sources.
Do both devices operate from the same supply voltage range?
Both the AD8220BRMZ and AD8221ARM operate from dual supplies of ±2.25 V to ±18 V (or single supply of 4.5 V to 36 V), allowing either device to be used in a wide range of industrial and instrumentation systems. Designers should still verify the exact specified supply range and output swing limitations in each datasheet for the target operating conditions.
Can the AD8220BRMZ and AD8221ARM be used interchangeably in an existing design?
They should not be treated as drop-in replacements. Although both are 8-lead MSOP instrumentation amplifiers with similar gain-setting architecture, differences in input bias current, offset voltage, offset drift, and noise characteristics mean that substituting one for the other requires revalidation of DC error budget, source impedance compatibility, and overall circuit performance against the manufacturer datasheets.