Part A
AD847ARZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 6367 PCS
- Package
- SOIC-8
- Series
- Linear - Amplifiers - Instrumentation, OP Amps, Buffer Amps
Replacement verdict
Not a drop-in replacement
The AD8479BRZ and AD847ARZ are not drop-in replacements for one another. Although both are precision analog devices in SOIC packages, they differ fundamentally in function, bandwidth, supply range, and input architecture, so the AD847ARZ cannot be substituted directly for the AD8479BRZ without circuit redesign and full validation.
Different device function
Different bandwidth
Different supply range
Different input architecture
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AD8479BRZ | AD847ARZ | Why it matters |
|---|---|---|---|
| Amplifier Type | Difference Amplifier | Operational Amplifier (High Speed) | The two parts serve fundamentally different functions; a difference amplifier extracts a differential signal, while a high-speed op amp is a general-purpose building block, so they are not direct substitutes. |
| Number of Circuits | 1 | 1 | Both are single-channel devices, so channel count does not differentiate them for substitution purposes. |
| Gain Bandwidth Product | Not specified (fixed gain difference amp) | 50 MHz | GBW determines the bandwidth available for a given closed-loop gain; the AD847ARZ offers wide small-signal bandwidth while the AD8479BRZ is a fixed-gain difference amplifier without a conventional GBW spec. |
| Slew Rate | Not specified | 300 V/µs | Slew rate limits large-signal response speed; the AD847ARZ is designed for fast large-signal swings, which the difference amplifier is not specified for. |
| Input Offset Voltage | ±0.5 mV (typical, referred to input) | ±0.5 mV (typical) | Offset voltage directly affects DC accuracy; both parts have comparable typical offset, but the AD8479BRZ's offset is specified in the context of high common-mode difference amplification. |
| Common-Mode Input Range | ±600 V | ±10 V (typical supply-limited) | The AD8479BRZ is specifically built to handle very high common-mode voltages, whereas the AD847ARZ is limited to its supply rails, making them unsuitable as substitutes in high-voltage sensing applications. |
| 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 AD847ARZ tolerates a slightly lower minimum supply, but both cover common bipolar rails. |
| Operating Temperature Range | -40°C to +125°C | -40°C to +85°C | The wider temperature range of the AD8479BRZ supports harsher environments, while the AD847ARZ is limited to standard industrial temperature ranges. |
| Package / Mounting | 8-SOIC (Surface Mount) | 8-SOIC (Surface Mount) | Both use the same 8-lead SOIC footprint, so board-level physical compatibility is maintained even though the electrical functions differ. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD847ARZ | AD8479BRZ |
|---|---|---|
| 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 AD8479BRZ and the AD847ARZ?
The AD8479BRZ is a high common-mode voltage difference amplifier designed to precisely measure signals with very high common-mode voltages (up to ±600 V), featuring a fixed gain of 1. The AD847ARZ is a high-speed, low-power operational amplifier with a 50 MHz gain-bandwidth product and a 300 V/µs slew rate, intended for general-purpose signal conditioning and amplification. They serve fundamentally different circuit functions and are not interchangeable.
Are the AD8479BRZ and AD847ARZ pin-compatible?
No. The AD8479BRZ is supplied in an 8-lead SOIC package with a pinout specific to a difference amplifier (including supply, reference, and differential input pins). The AD847ARZ is supplied in an 8-lead SOIC package with a standard single operational amplifier pinout (offset null, inverting input, non-inverting input, and output). The pin functions differ, so they cannot be dropped into the same PCB footprint.
Can the AD847ARZ be used to replace the AD8479BRZ in a high common-mode voltage measurement application?
No. The AD847ARZ is a standard operational amplifier and is not rated for the ±600 V common-mode input range of the AD8479BRZ. Using the AD847ARZ in such an application would exceed its absolute maximum input voltage ratings and would not provide the integrated precision resistor network required for accurate high-voltage difference measurement.
How do the supply voltage requirements of the AD8479BRZ and AD847ARZ compare?
The AD8479BRZ operates from dual supplies of ±5 V to ±18 V (or a single supply of 10 V to 36 V). The AD847ARZ operates from dual supplies of ±4.5 V to ±18 V. Both support a similar dual-supply range, but the AD8479BRZ is specified for operation with high common-mode voltages that are independent of its own supply rails.
What is the gain configuration of each device?
The AD8479BRZ has a fixed gain of 1 V/V, set internally by a precision resistor network; no external gain-setting components are required. The AD847ARZ is an uncompensated operational amplifier whose closed-loop gain is set by external feedback resistors, allowing user-defined gain configurations.
Which device is better suited for high-speed signal amplification?
The AD847ARZ is better suited for high-speed amplification, with a 50 MHz gain-bandwidth product and a 300 V/µs slew rate. The AD8479BRZ is optimized for precision high common-mode voltage difference measurement and has a much lower bandwidth (typically 480 kHz at gain of 1), making it unsuitable for high-speed signal paths.
Do both parts share the same operating temperature range?
Both the AD8479BRZ and the AD847ARZ are specified for the industrial temperature range of −40°C to +85°C. The "B" and "R" grade suffixes in the part numbers denote performance grades and package types, respectively, but both are rated for industrial-temperature operation per their respective datasheets.
What are the key precision specifications of the AD8479BRZ compared with the AD847ARZ?
The AD8479BRZ offers high precision for difference amplification, including a maximum input offset voltage of 1 mV, a typical common-mode rejection ratio (CMRR) of 90 dB, and a fixed gain error of 0.01%. The AD847ARZ, as a general-purpose op amp, has a maximum input offset voltage of 0.5 mV and is not characterized for high common-mode voltage rejection. The AD8479BRZ's integrated resistor network provides matched ratio performance that the AD847ARZ cannot achieve without external precision components.