Part A
AD8028ARZ
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 5537 PCS
- Package
- SOIC-8
- Series
- Amplificateurs linéaires - instruments, amplificateurs opérationnels, amplificateurs tampons
Replacement verdict
Not a drop-in replacement
The AD8028ARZ and AD8021AR are not drop-in replacements for one another. Although both are high-speed voltage-feedback operational amplifiers in SOIC-8 packages, they differ in channel count, supply voltage range, quiescent current, and bandwidth, so circuit-level validation is required before any substitution.
Different channel count
Different supply voltage range
Different quiescent current
Different bandwidth
Parts at a glance
Part B
AD8021AR
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 7274 PCS
- 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 | AD8028ARZ | AD8021AR | Why it matters |
|---|---|---|---|
| Number of Amplifiers | 2 | 1 | A dual versus single channel count changes board layout, package footprint, and channel density per design. |
| Gain Bandwidth Product | 190 MHz | 490 MHz | GBW determines the maximum signal frequency the amplifier can handle at a given closed-loop gain. |
| -3 dB Bandwidth (G=1) | 190 MHz | 200 MHz | Unity-gain bandwidth affects how fast small signals can be amplified without significant attenuation. |
| Slew Rate | 100 V/µs | 460 V/µs | Slew rate limits how quickly the output can respond to large signal steps, affecting large-signal distortion. |
| Input Voltage Noise Density | 4.3 nV/√Hz | 2.1 nV/√Hz | Lower input noise improves signal-to-noise ratio in precision and low-level signal applications. |
| Supply Voltage Range | 2.7 V to 12 V | 4.5 V to 24 V | The allowable supply range determines compatibility with the system power rails and output swing headroom. |
| Quiescent Current per Amplifier | 1.4 mA | 7.8 mA | Quiescent current directly impacts power consumption and thermal budget in the design. |
| Input Offset Voltage (Max) | 1 mV | 1 mV | Offset voltage affects DC accuracy; matching values indicate similar DC precision performance. |
| Package | 8-Lead SOIC | 8-Lead SOIC | Package compatibility determines whether the parts are drop-in interchangeable on an existing PCB footprint. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +85 °C | The temperature range defines suitability for industrial or extended-temperature environments. |
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 | AD8028ARZ | AD8021AR |
|---|---|---|
| Part Status | Active | Obsolete |
| Amplifier Type | General Purpose | Voltage Feedback |
| Number of Circuits | 2 | 1 |
| Slew Rate | 100V/µs | 460V/µs |
| Current - Input Bias | 4 µA | 7.5 µA |
| Voltage - Input Offset | 200 µV | 400 µV |
| Supply Current | 6.5mA (x2 Channels) | 7.8mA |
| Current - Output / Channel | 120 mA | 70 mA |
| Voltage - Supply Span (Min) | - | 4.5 V |
| Voltage - Supply Span (Max) | - | 24 V |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
| Base Product Number | - | AD8021 |
| -3 dB Bandwidth | 190 MHz | 560 MHz |
| Output Type | Rail-to-Rail | - |
| Voltage - Supply Span(Min) | 2.7 V | - |
| Voltage - Supply Span(Max) | 12 V | - |
Frequently asked questions
What are the primary differences between the AD8028ARZ and AD8021AR?
The AD8028ARZ is a dual, low-distortion, high-speed voltage feedback operational amplifier with rail-to-rail output, specified for operation on supplies from 2.7 V to 12 V. The AD8021AR is a single, high-speed, low-noise voltage feedback amplifier with an externally compensated gain, typically operated on ±5 V to ±12 V dual supplies. The AD8028ARZ integrates two amplifiers in a single 8-lead SOIC package, while the AD8021AR is a single amplifier in an 8-lead SOIC package.
Are the AD8028ARZ and AD8021AR pin-compatible in the SOIC-8 package?
No. Although both devices are offered in an 8-lead SOIC package, their pinouts differ. The AD8028ARZ (dual amplifier) uses the standard dual op-amp pinout with two amplifiers sharing supply and ground pins, whereas the AD8021AR (single amplifier) uses a single-amplifier pinout that includes dedicated compensation and offset-null pins. Therefore, they cannot be directly interchanged on the same PCB footprint without layout changes.
How do the supply voltage ranges of the AD8028ARZ and AD8021AR compare?
The AD8028ARZ is specified for single-supply operation from 2.7 V to 12 V (or dual supplies of ±1.35 V to ±6 V). The AD8021AR is specified for dual-supply operation typically from ±5 V to ±12 V. The AD8028ARZ therefore supports lower supply voltages and single-supply designs, while the AD8021AR is intended for higher-voltage dual-supply applications.
Which device offers lower input voltage noise?
The AD8021AR is characterized by a low input voltage noise density of approximately 2.1 nV/√Hz at 10 kHz, making it suitable for low-noise signal conditioning. The AD8028ARZ has a higher input voltage noise density, typically around 4.5 nV/√Hz at 1 kHz. For noise-sensitive applications, the AD8021AR provides the lower noise floor.
How does the gain bandwidth and compensation differ between the two amplifiers?
The AD8021AR features an externally compensated architecture, allowing the user to set the compensation capacitor to trade bandwidth for stability and gain, with a typical gain bandwidth product of 490 MHz when optimally compensated. The AD8028ARZ is internally compensated and provides a fixed gain bandwidth of approximately 190 MHz. The AD8021AR offers greater flexibility for high-gain configurations, while the AD8028ARZ simplifies design with fixed internal compensation.
Can the AD8028ARZ drive rail-to-rail outputs while the AD8021AR cannot?
Yes. The AD8028ARZ features a rail-to-rail output stage, allowing the output voltage to swing close to both supply rails, which is advantageous in low-voltage single-supply systems. The AD8021AR does not have a rail-to-rail output; its output swing is limited to within approximately 1 V of each supply rail, depending on load conditions. This difference affects headroom and dynamic range in low-voltage designs.
Which device is better suited for portable or low-power applications?
The AD8028ARZ is generally better suited for portable and low-voltage applications because it operates from supplies as low as 2.7 V and is a dual amplifier, reducing board space and component count. The AD8021AR requires higher supply voltages (typically ±5 V minimum) and is a single amplifier, making it less ideal for low-voltage portable designs. Designers should verify quiescent current from the respective datasheets for their specific operating conditions.
Are the AD8028ARZ and AD8021AR interchangeable in existing designs without requalification?
No. Due to differences in pinout, supply voltage range, compensation architecture, output swing, and package pin functions, the two devices are not drop-in replacements. Any substitution requires a review of the PCB layout, supply rails, compensation network, and overall circuit performance against the manufacturer datasheets, followed by appropriate requalification testing.