RS8551
Zero-drift precision op-amp with 5μV max offset voltage, 4.5MHz GBW, and 20μA supply current for high-accuracy applic...
Product Overview
Description
The RS8551 is a zero-drift precision operational amplifier featuring auto-zero calibration to achieve 5μV maximum offset voltage.
With 4.5MHz gain-bandwidth product and 2.5V/μs slew rate, it provides excellent AC performance while maintaining DC precision.
The device operates from 2.7V to 5.5V single supply and consumes only 20μA per amplifier, making it ideal for portable instrumentation.
Product Series
RS
Primary Application
Precision sensor conditioning
Key Features
- 5μV max offset voltage with auto-zero
- 0.01μV/°C offset drift
- 4.5MHz GBW for good AC performance
- Low 20μA supply current
- Rail-to-rail input and output
- Pin-compatible with OPA189
Specifications
| Offset Voltage | 5 μV (max) |
|---|---|
| Offset Drift | 0.01 μV/°C |
| GBW | 4.5 MHz |
| Slew Rate | 2.5 V/μs |
| Supply Current | 20 μA |
| Noise | 25 nV/√Hz |
| Supply Voltage | 2.7 - 5.5 V |
| Package | SOT23-5, MSOP-8 |
Applications
Precision sensor conditioning
Sensor signal conditioning
Current sensing
Electronic system design
Strain gauge amplifiers
Electronic system design
Thermocouple amplifiers
Electronic system design
Medical instrumentation
Medical electronics
FAE Expert Insights
"The RS8551 has become my go-to recommendation for precision applications requiring zero-drift performance. I've used it in numerous current sensing and sensor conditioning designs, and it consistently delivers the advertised 5μV offset. The auto-zero architecture effectively eliminates 1/f noise, which is crucial for low-frequency measurements. What impresses me most is the combination of precision and reasonable power consumption - 20μA is excellent for a zero-drift op-amp. The pin-compatibility with OPA189 makes it an easy drop-in replacement with significant cost savings. For high-side current sensing with gains of 50-100, this op-amp's low offset minimizes the error contribution."
Excellent zero-drift performance with 5μV offset at competitive cost
— Dr. Wang Wei, BeiLuo
Frequently Asked Questions
How does the auto-zero calibration work in RS8551?
The RS8551 uses an auto-zero calibration technique that continuously corrects offset voltage: (1) Internal switches alternate between normal operation and calibration phases at ~10kHz; (2) During calibration, the offset is measured and stored on internal capacitors; (3) During normal operation, this correction is applied to cancel the offset; (4) The result is effective elimination of DC offset and 1/f noise. The calibration is transparent to the user and requires no external components. The switching creates small charge injection glitches, but these are filtered internally and typically don't affect the application.
No user intervention required. The auto-zero operates automatically. Just ensure power supply bypassing is adequate.
What is the recommended PCB layout for RS8551?
For optimal RS8551 performance: (1) Place 0.1μF ceramic bypass capacitor within 2mm of each supply pin; (2) Use solid ground plane under the op-amp for noise shielding; (3) Keep input traces short and away from digital/high-current traces; (4) Use guard rings around input pins for high-impedance applications (>1MΩ); (5) Minimize thermocouple effects by keeping copper areas symmetrical. For precision applications, pay special attention to solder joints and connector thermal EMF. The auto-zero architecture helps reject some of these errors, but good layout practices still matter.
Follow standard precision analog layout practices. Use guard rings for high-impedance sensor interfaces.
Can RS8551 be used for high-side current sensing?
Yes, the RS8551 is excellent for high-side current sensing: (1) Rail-to-rail input allows operation at supply voltage; (2) Low 5μV offset minimizes error at low sense voltages; (3) 4.5MHz GBW provides fast response for current limiting; (4) 20μA current consumption is suitable for battery applications. For a typical 100mΩ sense resistor at 1A, the 100mV signal with 5μV offset error gives 0.005% accuracy. The auto-zero feature maintains this accuracy over temperature. Use a differential amplifier configuration with matched resistors for best CMRR.
Use differential configuration with 0.1% resistors. Place sense resistor close to op-amp inputs.
What is the noise performance of RS8551?
The RS8551 has excellent noise performance: (1) Voltage noise density - 25nV/√Hz at 1kHz; (2) Low 1/f noise corner - ~100Hz due to auto-zero; (3) Current noise - 5fA/√Hz (negligible for most applications); (4) 0.1-10Hz peak-to-peak noise - 0.5μVpp. The auto-zero architecture effectively eliminates 1/f (flicker) noise, which is a major advantage for DC and low-frequency applications. For a 1kHz bandwidth, total noise is approximately 0.8μVrms. This is excellent for a zero-drift op-amp and comparable to or better than competing devices.
The low 1/f noise makes RS8551 ideal for low-frequency sensor applications. Calculate total noise for your bandwidth.
How does RS8551 compare to chopper-stabilized op-amps?
RS8551 uses auto-zero rather than traditional chopper stabilization: (1) Auto-zero has lower switching noise/intermodulation than chopper; (2) Both achieve similar offset voltage (5μV range); (3) Auto-zero typically has wider bandwidth for the same power; (4) Chopper may have slightly better offset drift in some cases; (5) Auto-zero is generally preferred for applications sensitive to switching artifacts. The RS8551's auto-zero implementation is optimized to minimize charge injection and switching noise, making it suitable for precision measurement applications where chopper noise might be problematic.
Choose RS8551 for applications sensitive to switching noise. Both architectures provide excellent DC precision.