Part A
AD847ARZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 6367 PCS
- Package
- SOIC-8
- Series
- Linear - Amplificadores - Instrumentação, OP Amps, Buffer Amps
Replacement verdict
Not a drop-in replacement
The AD8479ARZ and AD847ARZ are not drop-in replacements for one another. Although both are precision analog devices in SOIC-8 packages, they differ fundamentally in function, input architecture, and supply requirements, so substituting one for the other requires circuit redesign and full validation.
Different amplifier function
Different input topology
Different supply range
Different gain configuration
Parts at a glance
Part B
AD8479ARZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 1516 PCS
- Package
- SOIC-8
- Series
- Linear - Amplificadores - Instrumentação, 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 | AD8479ARZ | AD847ARZ | Why it matters |
|---|---|---|---|
| Amplifier Type | Difference Amplifier | General Purpose Amplifier | Defines the core function; a difference amplifier measures differential signals with high common-mode rejection, while a general-purpose op amp is a building block for many topologies, so they are not directly substitutable. |
| Number of Circuits | 1 | 1 | Both are single-channel devices, so channel count is not a differentiator for substitutability. |
| Gain Configuration | Fixed gain of 1 (unity) | External resistor programmable | A fixed unity-gain difference amplifier cannot be reconfigured for other gains, whereas the AD847 gain is set by external resistors, giving far greater design flexibility. |
| Input Offset Voltage (max) | ±1 mV (typical, RTI) | ±0.5 mV (typical) | Lower offset improves DC accuracy; the AD847 offers tighter offset, which matters for precision signal chains. |
| Gain Bandwidth Product | 130 kHz | 50 MHz | Bandwidth determines the maximum signal frequency the amplifier can handle; the AD847 is far faster, so it suits high-speed applications the AD8479 cannot serve. |
| Slew Rate | 0.5 V/µs | 300 V/µs | Slew rate limits large-signal transient response; the AD847's much higher slew rate enables fast, large-signal operation not possible with the AD8479. |
| Common-Mode Input Range | ±600 V | Limited to supply rails | The AD8479 tolerates very high common-mode voltages, making it suitable for high-voltage sensing; the AD847 cannot survive such conditions. |
| Supply Voltage Range | ±5 V to ±18 V (dual) | ±4.5 V to ±18 V (dual) | Supply range affects compatibility with the system power rails; the AD847 works at slightly lower minimum supplies. |
| Package / Mounting | 8-Lead SOIC (surface mount) | 8-Lead SOIC (surface mount) | Identical package and footprint allow drop-in board placement, though electrical differences still prevent direct substitution. |
| Operating Temperature Range | −40 °C to +125 °C | −40 °C to +85 °C | The wider temperature range of the AD8479 supports harsher environments where the AD847 is not rated. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD847ARZ | AD8479ARZ |
|---|---|---|
| Part Status | Active | Active |
| Amplifier Type | General Purpose | General Purpose |
| Number of Circuits | 1 | 1 |
| Slew Rate | 300V/µs | 8V/µs |
| Gain Bandwidth Product | 50 MHz | - |
| Current - Input Bias | 3.3 µA | - |
| Voltage - Input Offset | 500 µV | 500 µV |
| Supply Current | 5.3mA | 550µA |
| Current - Output / Channel | 32 mA | 55 mA |
| Voltage - Supply Span(Min) | 9 V | 5 V |
| Voltage - Supply Span(Max) | 36 V | 36 V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Output Type | - | Rail-to-Rail |
| -3 dB Bandwidth | - | 130 kHz |
Frequently asked questions
What are the primary functional differences between the AD8479ARZ and the AD847ARZ?
The AD8479ARZ is a precision, high common-mode voltage difference amplifier designed to amplify small differential signals riding on very high common-mode voltages (up to ±600 V), while the AD847ARZ is a high-speed, low-power operational amplifier. They serve fundamentally different signal-conditioning roles and are not functionally interchangeable.
Are the AD8479ARZ and AD847ARZ pin-compatible in the same package?
Both devices are offered in an 8-lead SOIC package (the "RZ" suffix denotes RoHS-compliant SOIC), but their pin functions and internal architectures differ. The AD8479ARZ is a fixed-gain difference amplifier with dedicated REF and supply pins, whereas the AD847ARZ is a general-purpose op amp with standard inverting, non-inverting, and offset-null pins. Pin-compatibility alone does not permit substitution.
Can the AD8479ARZ be used as a drop-in replacement for the AD847ARZ in an existing design?
No. The AD8479ARZ is a fixed-gain (G = 1) difference amplifier intended for high common-mode voltage sensing, while the AD847ARZ is a high-speed op amp requiring external feedback for gain configuration. Their input structures, supply requirements, and transfer functions differ, so a direct replacement is not valid without redesign and verification against the respective datasheets.
How do the supply voltage requirements of the AD8479ARZ and AD847ARZ compare?
The AD8479ARZ operates from dual supplies typically in the ±5 V to ±18 V range, with its high common-mode input capability tied to the supply rails. The AD847ARZ is specified for operation on ±5 V to ±15 V dual supplies. Designers must confirm the exact supply range and headroom requirements in each device's official datasheet before use.
Which device is better suited for high common-mode voltage measurement?
The AD8479ARZ is specifically designed for this application, handling common-mode voltages up to ±600 V while amplifying the differential signal. The AD847ARZ is a conventional op amp and is not rated for high common-mode voltage sensing, so it is unsuitable for that function without additional external circuitry.
How do the bandwidth and speed characteristics of the two parts differ?
The AD847ARZ is a high-speed op amp with a specified unity-gain bandwidth and slew rate intended for fast signal processing. The AD8479ARZ, as a precision difference amplifier, has a comparatively lower bandwidth optimized for accuracy in high common-mode sensing. Exact bandwidth and slew-rate figures should be taken from the respective manufacturer datasheets.
Do both parts share the same operating temperature range and qualification grade?
Both the AD8479ARZ and AD847ARZ are industrial-grade parts offered in the same 8-lead SOIC package with an "RZ" RoHS-compliant suffix. Their specified operating temperature ranges and qualification details should be verified individually in the official Analog Devices datasheets, as the two product families may differ in detailed grade specifications.