OPA37 Ultra-Low Noise Precision Operational Amplifier

Overview

The OPA37 is an ultra-low noise, high-precision operational amplifier designed for applications requiring exceptional signal integrity and accuracy. This device combines extremely low noise performance with outstanding DC precision, making it ideal for sensitive instrumentation and measurement systems. The OPA37 is pin-compatible with industry-standard operational amplifiers like the OP-07, OP-05, AD510, and AD517, allowing for easy upgrades in existing designs.

Key Features

• Ultra-Low Noise: 4.5nV/√Hz maximum at 1kHz
• Precision DC Performance: 100µV maximum offset voltage
• Excellent Temperature Stability: 0.4µV/°C maximum drift
• High Gain: 117dB minimum open-loop gain
• Superior Rejection Ratios: 100dB minimum CMRR, 94dB minimum PSRR
• Wide Supply Range: Operates from ±4V to ±18V supplies
• Industry-Standard Pinout: Compatible with OP-07, OP-05, AD510, AD517 sockets

Applications

The OPA37's exceptional combination of low noise and high precision makes it suitable for demanding applications including:

• Precision Instrumentation: High-accuracy measurement systems
• Data Acquisition: Front-end signal conditioning for ADCs
• Test Equipment: Precision signal sources and measurement circuits
• Professional Audio Equipment: Low-noise microphone preamplifiers
• Transducer Amplifiers: Bridge amplifiers for strain gauges and load cells
• Radiation-Hard Equipment: Suitable for aerospace and nuclear applications
• Medical Instrumentation: ECG amplifiers and other sensitive biomedical circuits

Electrical Characteristics

All specifications are typical at +25°C and ±15V supplies unless otherwise noted.

DC Characteristics

• Input Offset Voltage: 25µV (typ), 100µV (max)
• Input Offset Voltage Drift: 0.2µV/°C (typ), 0.4µV/°C (max)
• Input Bias Current: 10nA (typ), 50nA (max)
• Input Offset Current: 2nA (typ), 15nA (max)
• Open-Loop Gain: 130dB (typ), 117dB (min)
• Common-Mode Rejection Ratio: 120dB (typ), 100dB (min)
• Power Supply Rejection Ratio: 110dB (typ), 94dB (min)

AC Characteristics

• Input Voltage Noise: 3.8nV/√Hz at 1kHz (typ), 4.5nV/√Hz (max)
• Current Noise: 0.4pA/√Hz at 1kHz
• Gain Bandwidth Product: 8MHz (typ)
• Slew Rate: 2.3V/µs (typ)
• Settling Time (0.01%): 3µs for 10V step (typ)

Power Characteristics

• Supply Voltage Range: ±4V to ±18V
• Quiescent Current: 4.5mA per amplifier (typ)
• Operating Temperature Range: -55°C to +125°C

Package Information

The OPA37 is available in several industry-standard packages:

8-Pin Plastic DIP (P Package)

• Package Dimensions: 9.81mm x 6.35mm
• Lead Pitch: 2.54mm
• Operating Temperature: -55°C to +125°C

8-Pin SOIC (D Package)

• Package Dimensions: 4.90mm x 3.91mm
• Lead Pitch: 1.27mm
• Operating Temperature: -55°C to +125°C

TO-99 Metal Can (H Package)

• Package Dimensions: 9.08mm diameter
• Lead Configuration: 8-lead radial
• Operating Temperature: -55°C to +125°C

Design Considerations

When implementing the OPA37 in precision circuits, consider the following:

Noise Optimization

To achieve the lowest possible noise performance:

• Use low-impedance feedback networks to minimize current noise contribution
• Implement proper grounding and shielding techniques
• Consider power supply filtering to reduce high-frequency noise

Thermal Management

For best DC precision:

• Minimize thermal gradients across the package
• Consider using a thermal pad or heat sink in high-precision applications
• Allow sufficient warm-up time for critical measurements

Stability Considerations

The OPA37's high gain bandwidth requires attention to:

• Proper compensation for capacitive loads
• Careful PCB layout to minimize parasitic capacitance
• Use of appropriate feedback network values

Conclusion

The OPA37 operational amplifier sets the standard for ultra-low noise precision amplification. Its combination of sub-5nV/√Hz noise, microvolt-level offset voltage, and excellent drift characteristics make it the ideal choice for the most demanding instrumentation and measurement applications. The device's compatibility with industry-standard packages and pinouts allows for easy implementation in both new designs and upgrades to existing systems.