PSA2002
Low-noise instrumentation amplifier with high CMRR, single-resistor gain setting, excellent DC accuracy
Product Overview
Description
The PSA2002 is a precision instrumentation amplifier featuring high common-mode rejection ratio (CMRR) of 120dB and low noise of 8nV/√Hz.
With single-resistor gain programming from 1 to 1000 and excellent DC accuracy, this amplifier is ideal for bridge sensors, strain gauges, and differential sensor interfaces.
The device features low offset voltage of 25uV, low offset drift of 0.1uV/°C, and rail-to-rail output for maximum dynamic range.
Product Series
PSA
Primary Application
Bridge sensor interfaces
Key Features
- High CMRR: 120dB minimum
- Single-resistor gain programming
- Low noise: 8nV/√Hz
- Low offset voltage: 25uV max
- Low gain error: 0.05%
- Rail-to-rail output
- Wide gain range: 1 to 1000
- Low offset drift: 0.1uV/°C
- Reference pin for output level shifting
Specifications
| Gain Range | 1 to 1000 |
|---|---|
| Gain Error | 0.05% |
| Offset Voltage | 25uV max |
| Offset Drift | 0.1uV/°C |
| CMRR | 120dB min |
| Noise Density | 8nV/√Hz @ 1kHz |
| Bandwidth | 800kHz at Gain=1 |
| Slew Rate | 0.5V/us |
| Input Bias Current | 2nA max |
| Supply Voltage | 2.7V - 5.5V single, ±1.35V - ±2.75V dual |
| Temperature Range | -40°C to +85°C (Industrial), -40°C to +125°C (Automotive) |
| Package | SOIC-8, MSOP-8, DFN-8 |
Applications
Bridge sensor interfaces
Sensor signal conditioning
Strain gauge amplifiers
Electronic system design
Pressure sensor conditioning
Sensor signal conditioning
Weigh scale systems
Electronic system design
Temperature measurement
Data acquisition and conversion
Industrial process control
Industrial automation and control
Medical instrumentation
Medical electronics
FAE Expert Insights
"The PSA2002 is my top recommendation for bridge sensor applications. The 120dB CMRR effectively rejects common-mode noise in industrial environments, allowing accurate measurement of small differential signals. I've used this amplifier in weigh scale designs where the single-resistor gain setting simplifies calibration - just change one resistor to adjust the scale range. The low noise of 8nV/√Hz is excellent for instrumentation amplifiers and supports high-resolution measurement. The reference pin is useful for level-shifting the output to match ADC input ranges. For best CMRR, I recommend using balanced source resistances and keeping input traces symmetric."
High CMRR with simple single-resistor gain programming
— Thomas Wu, BeiLuo
Frequently Asked Questions
How do I set the gain of the PSA2002?
The PSA2002 gain is set using a single external resistor connected between the RG pins. The gain formula is: Gain = 1 + (100kΩ/Rg). For example, for a gain of 100, use Rg = 1.01kΩ. For a gain of 1000, use Rg = 100Ω. Use 0.1% tolerance resistors for accurate gain. The gain can be changed dynamically using a digital potentiometer or analog switch to select different resistors. The gain setting affects bandwidth - higher gains result in lower bandwidth (gain-bandwidth product is constant at approximately 800kHz).
Calculate Rg based on required gain using the formula. Use precision resistors for accurate gain. Contact our FAE team for programmable gain configurations.
What is the reference pin used for?
The reference (REF) pin allows level-shifting of the output voltage. The output voltage is referenced to the voltage applied at the REF pin rather than ground. This is useful for: 1) Matching the ADC input range (e.g., shifting to 2.5V for a 0-5V ADC); 2) Implementing differential output by driving REF with an inverted signal; 3) Rejecting common-mode offsets in the signal chain. The REF pin should be driven by a low-impedance source, typically a voltage reference or op-amp buffer. For best CMRR, keep the REF pin quiet and well-decoupled.
Use REF pin to center output in ADC range. Buffer the reference voltage with an op-amp for best performance.
How does the CMRR vary with frequency?
CMRR typically decreases with increasing frequency due to parasitic capacitances in the input stage. The PSA2002 maintains 120dB CMRR at DC and low frequencies, decreasing to approximately 80dB at 10kHz. This is still excellent rejection for most applications. For high-frequency common-mode noise, additional external filtering may be needed. The CMRR is also affected by source impedance imbalance - ensure both input source resistances are matched for best CMRR. A 1% imbalance in source resistance can reduce CMRR by 40dB.
Match source impedances for best CMRR. Add external filtering for high-frequency common-mode noise. Contact our FAE team for high-CMRR design techniques.
Can I use the PSA2002 with single supply?
Yes, the PSA2002 operates from single supplies of 2.7V to 5.5V. For single-supply operation, the inputs must be biased within the common-mode range (typically 0.5V to Vcc-0.5V). Bridge sensors powered from the same supply naturally satisfy this requirement. The output can swing rail-to-rail, maximizing dynamic range. Use the REF pin to set the output quiescent level, typically at mid-supply (Vcc/2) for maximum symmetrical swing. Ensure the reference voltage is well-decoupled and stable.
Use single supply for battery-powered applications. Bias REF at mid-supply for maximum output swing. Contact our FAE team for single-supply design guidance.
What are the key differences between an instrumentation amplifier and a standard op-amp difference amplifier?
Instrumentation amplifiers (INAs) offer several advantages over op-amp difference amplifiers: 1) Much higher input impedance (GΩ vs kΩ) eliminates loading on sensor bridges; 2) Better CMRR (120dB vs 60-80dB typical) for superior noise rejection; 3) Single-resistor gain setting vs multiple resistors required for op-amp circuits; 4) Better gain accuracy (0.05% vs 1% typical) due to integrated matched resistors; 5) Lower offset drift due to integrated laser-trimmed resistors. The trade-off is higher cost and power consumption. For precision sensor applications, INAs provide superior performance with simpler design.
Use INAs for precision sensor interfaces requiring high CMRR and accuracy. Use op-amp difference amplifiers for cost-sensitive, less critical applications.