Part A
AD8479ARZ
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 1516 PCS
- Package
- SOIC-8
- Series
- Amplificateurs linéaires - instruments, amplificateurs opérationnels, amplificateurs tampons
Replacement verdict
Not a drop-in replacement
The AD8479ARZ and AD847JR are not functionally interchangeable. The AD8479ARZ is a precision high common-mode voltage difference amplifier, while the AD847JR is a high-speed operational amplifier; their core functions, input structures, and application roles differ fundamentally, so the AD847JR cannot serve as a direct substitute in AD8479ARZ circuits.
Different amplifier function
Different input topology
Different bandwidth class
Different application role
Parts at a glance
Part B
AD847JR
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 125 PCS
- Package
- SOIC-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 | AD8479ARZ | AD847JR | Why it matters |
|---|---|---|---|
| Amplifier Type | Difference Amplifier | General Purpose Operational Amplifier | The two parts serve fundamentally different functions; a difference amplifier extracts a differential signal with high common-mode rejection, while a general-purpose op-amp is a building block for many circuit topologies, so they are not directly substitutable. |
| Number of Channels | 1 | 1 | Both are single-channel devices, so channel count alone does not differentiate them, but it confirms neither offers multi-channel integration. |
| Input Offset Voltage (max) | ±1 mV (typical, referred to input) | ±0.5 mV (typical) | Offset voltage directly limits DC accuracy; a lower offset reduces measurement error in precision signal chains. |
| Gain Configuration | Fixed gain of 1 (unity) | External resistor-set gain (open-loop op-amp) | A fixed-gain difference amplifier provides a defined transfer function out of the box, whereas an op-amp requires external feedback components to set gain, affecting design effort and flexibility. |
| Common-Mode Input Range | Very wide, extends well beyond supply rails (±600 V capable) | Limited to approximately the supply rails | The wide common-mode range of the difference amplifier allows high-voltage sensing, which a standard op-amp cannot handle without additional circuitry. |
| Supply Voltage Range | ±5 V to ±18 V (dual supply) | ±4.5 V to ±18 V (dual supply) | Supply range determines compatibility with the system power rails; slight differences affect low-voltage operation margins. |
| Gain Bandwidth Product | Approximately 1 MHz (fixed gain) | Approximately 50 MHz | Bandwidth governs the maximum signal frequency the device can process; the op-amp offers much higher bandwidth for high-speed signal conditioning. |
| Package | 8-Lead SOIC | 8-Lead SOIC | Matching package footprints simplify board-level replacement, 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 difference amplifier suits harsher environments, while the op-amp is limited to standard industrial conditions. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD8479ARZ | AD847JR |
|---|---|---|
| Supplier | - | Analog Devices Inc.,Rochester Electronics, LLC |
| Part Status | Active | Obsolete |
| Amplifier Type | General Purpose | General Purpose |
| Number of Circuits | 1 | 1 |
| Slew Rate | 8V/µs | 300V/µs |
| Gain Bandwidth Product | - | 50 MHz |
| Current - Input Bias | - | 3.3 µA |
| Voltage - Input Offset | 500 µV | 500 µV |
| Supply Current | 550µA | 5.3mA |
| Current - Output / Channel | 55 mA | 32 mA |
| Voltage - Supply Span(Min) | 5 V | 9 V |
| Voltage - Supply Span(Max) | 36 V | 36 V |
| Operating Temperature | -40°C ~ 125°C | 0°C ~ 70°C |
| Mounting Type | Surface Mount | Surface Mount |
| Output Type | Rail-to-Rail | - |
| -3 dB Bandwidth | 130 kHz | - |
Frequently asked questions
What are the fundamental differences between the AD8479ARZ and the AD847JR?
The AD8479ARZ is a precision, high common-mode voltage difference amplifier designed to measure signals with common-mode voltages up to ±600 V, featuring a fixed gain of 1 and a differential input range of ±600 V. The AD847JR is a general-purpose, low-power operational amplifier with a 50 MHz gain-bandwidth product and a 300 V/µs slew rate, intended for conventional signal conditioning rather than high-voltage difference measurement.
Are the AD8479ARZ and AD847JR pin-compatible or interchangeable?
No. The AD8479ARZ is supplied in an 8-lead SOIC package configured as a difference amplifier with dedicated +IN, -IN, REF, and output pins, while the AD847JR is supplied in an 8-lead SOIC package configured as a standard op amp with IN+, IN-, and offset null pins. Their pin functions and internal topologies differ, so they are not direct substitutes.
How do the input common-mode voltage ranges of the two devices compare?
The AD8479ARZ supports a very wide common-mode input range of ±600 V, allowing it to interface directly with high-voltage rails and shunt-based current sensing in motor and power systems. The AD847JR is a conventional op amp whose input common-mode range is limited to its supply rails (typically ±5 V to ±15 V), so it cannot be used directly in high common-mode voltage applications.
What are the gain configurations of the AD8479ARZ and AD847JR?
The AD8479ARZ is a fixed-gain difference amplifier with a gain of 1 V/V, set internally and not user-adjustable. The AD847JR is an uncompensated-voltage-feedback op amp whose closed-loop gain is set externally by the user's feedback network, allowing arbitrary gain configurations within its bandwidth and stability limits.
How do the bandwidth and dynamic performance specifications differ?
The AD8479ARZ has a bandwidth of approximately 480 kHz at unity gain, optimized for accurate DC and low-frequency high-voltage difference measurements. The AD847JR offers a 50 MHz gain-bandwidth product and a 300 V/µs slew rate, making it suitable for higher-frequency signal processing where high common-mode voltage rejection is not required.
Which device is better suited for high-voltage current sensing applications?
The AD8479ARZ is specifically designed for high-voltage current sensing, with its ±600 V common-mode range and precision resistor network enabling direct measurement across high-side shunts without additional isolation or attenuation circuitry. The AD847JR is not rated for high common-mode voltages and would require external level-shifting or isolation, making it unsuitable as a direct high-side current-sense amplifier.
How do the supply voltage and power consumption requirements compare?
The AD8479ARZ operates from dual supplies of ±5 V to ±18 V and draws approximately 1.5 mA of quiescent current. The AD847JR operates from dual supplies of ±5 V to ±15 V with a typical quiescent current of about 5.5 mA, reflecting its higher bandwidth and slew-rate capability.
What are the typical accuracy and offset specifications for each device?
The AD8479ARZ features a maximum input offset voltage of 1 mV and a gain error of 0.02%, with a common-mode rejection ratio of at least 90 dB, supporting precision high-voltage measurements. The AD847JR has a typical input offset voltage of 0.5 mV and is not characterized for high common-mode rejection, as it is a general-purpose op amp rather than a precision difference amplifier.