Part A
AD847AR
ADI公司
- Lifecycle
- Active
- Stock
- 7655 件
- Series
- Linear - Amplifiers - Instrumentation, Op Amps, Buffer Amps
Replacement verdict
Not a drop-in replacement
The AD8479ARZ and AD847AR are not functionally interchangeable. The AD8479ARZ is a precision high common-mode voltage difference amplifier with a fixed gain of 1 and a ±600 V common-mode input range, while the AD847AR is a high-speed low-power operational amplifier with a 50 MHz gain-bandwidth product. Their amplifier topology, input structure, gain configuration, and application roles differ fundamentally, so the AD847AR cannot serve as a substitute for the AD8479ARZ in high common-mode voltage sensing applications.
Different amplifier topology
Different input voltage range
Different gain configuration
Different application role
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 | AD847AR | Why it matters |
|---|---|---|---|
| Amplifier Type | Difference Amplifier | Voltage Feedback Amplifier | The two parts serve fundamentally different functions; a difference amplifier extracts a differential signal, while a voltage feedback op amp is a general-purpose building block, so they are not direct substitutes. |
| Number of Channels | 1 | 1 | Both are single-channel devices, so channel count does not differentiate them for single-signal designs. |
| Input Offset Voltage (max) | ±1 mV (typical, RTI) | ±0.5 mV (typical) | Offset voltage directly limits DC accuracy; lower offset reduces measurement error in precision signal chains. |
| Gain Bandwidth Product | 130 kHz (fixed gain = 1) | 50 MHz | Bandwidth determines the maximum signal frequency the part can handle; the AD847AR supports much higher-frequency signals than the AD8479ARZ. |
| Fixed Gain | 1 (unity, factory-set) | Configurable (external resistors) | The AD8479ARZ has a fixed unity gain, while the AD847AR gain is set by the user, affecting design flexibility and external component count. |
| Common-Mode Input Range | ±600 V | Limited by supply rails (approx. ±Vs) | The AD8479ARZ tolerates very high common-mode voltages, making it suitable for high-voltage sensing, whereas the AD847AR is limited to near its supply rails. |
| 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; both support similar bipolar supplies but differ slightly at the low end. |
| Input Bias Current (typical) | ±1 nA | ±3.5 µA | Lower input bias current reduces errors in high-impedance source applications; the AD8479ARZ is far superior here. |
| Package | 8-Lead SOIC | 8-Lead SOIC | Matching package and pinout simplifies 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 AD8479ARZ suits harsher environments, while the AD847AR is limited to standard industrial temperatures. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD847AR | AD8479ARZ |
|---|---|---|
| Part Status | Obsolete | Active |
| Base Product Number | AD847 | - |
| Amplifier Type | Standard (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 |
| Voltage - Supply Span (Min) | 9 V | - |
| Voltage - Supply Span (Max) | 36 V | - |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Packaging | Tube | - |
| Current - Output / Channel | 32 mA | 55 mA |
| Output Type | - | Rail-to-Rail |
| -3 dB Bandwidth | - | 130 kHz |
| Voltage - Supply Span(Min) | - | 5 V |
| Voltage - Supply Span(Max) | - | 36 V |
Frequently asked questions
What are the primary functional differences between the AD8479ARZ and the AD847AR?
The AD8479ARZ is a precision, high common-mode voltage difference amplifier designed for applications requiring a very high input common-mode voltage range (up to ±600 V), whereas the AD847AR is a high-speed, low-power operational amplifier. The AD8479ARZ integrates a precision resistor network to attenuate high common-mode voltages, while the AD847AR is a general-purpose op amp intended for signal conditioning and amplification within standard supply rails.
Are the AD8479ARZ and AD847AR pin-compatible or package-compatible?
No. The AD8479ARZ is supplied in an 8-lead SOIC package (SOIC-8), while the AD847AR is supplied in an 8-lead PDIP (N) or 8-lead SOIC (R) package depending on the specific grade. Even where both are offered in SOIC-8, the pin functions differ: the AD8479ARZ pinout includes dedicated REF and sense connections for its difference amplifier architecture, whereas the AD847AR follows a standard single op amp pinout. They are not direct drop-in replacements.
Can the AD8479ARZ be used as a direct substitute for the AD847AR in an existing design?
No. The two devices have different architectures, pinouts, and intended applications. The AD8479ARZ is a fixed-gain difference amplifier with an integrated resistor network and a high common-mode input range, while the AD847AR is a unity-gain-stable voltage feedback op amp. Substitution would require redesign of the surrounding circuit, including feedback networks and supply considerations, and is not supported as a direct replacement.
What are the key AC performance specifications of the AD847AR?
The AD847AR is a high-speed op amp with a typical unity-gain bandwidth of 50 MHz and a slew rate of 300 V/µs. It is specified for low power operation and is stable for gains of 1 or greater. These parameters make it suitable for video and high-speed signal processing applications, in contrast to the AD8479ARZ, which is optimized for precision DC and low-frequency high common-mode voltage measurement.
What is the input common-mode voltage range of the AD8479ARZ?
The AD8479ARZ is specified to handle input common-mode voltages up to ±600 V, which is its primary distinguishing feature. This wide range allows it to interface directly with high-voltage rails in motor control, power monitoring, and industrial systems without additional attenuation. The AD847AR does not offer this capability and is limited to its supply rail voltages.
Do the AD8479ARZ and AD847AR share the same supply voltage requirements?
No. The AD8479ARZ operates from dual supplies typically ranging from ±2.5 V to ±18 V (or a single supply of 5 V to 36 V), with the high common-mode range maintained independently of the supply. The AD847AR is specified for operation on ±5 V to ±15 V dual supplies. Designers must verify supply compatibility against the respective datasheets before considering any substitution.
Which device is better suited for high-voltage current sensing applications?
The AD8479ARZ is the appropriate choice for high-voltage current sensing because its ±600 V common-mode input range and integrated precision resistor network allow direct connection across high-side shunts in high-voltage systems. The AD847AR, as a standard op amp, would require external level shifting and attenuation circuitry and is not specified for direct high common-mode voltage sensing.