A very low noise, high accuracy, programmable voltage source for low frequency noise measurements

Area of Science:

• Electrical Engineering
• Instrumentation and Measurement

Background:

• Accurate low-frequency noise measurements require stable, low-noise voltage sources.
• Standard digital-to-analog converters (DACs) introduce noise that can corrupt sensitive measurements.
• Supercapacitors offer filtering benefits but suffer from leakage currents causing DC errors.

Purpose of the Study:

• To design a programmable voltage source with very low noise and high accuracy for low-frequency noise measurements.
• To overcome the DC error limitations caused by supercapacitor leakage currents.
• To achieve noise levels comparable to high-quality operational amplifiers.

Main Methods:

• Implementation of a supercapacitor-based two-pole low-pass filter to attenuate DAC noise below 100 mHz.
• Development of a specialized circuit topology to mitigate DC errors from supercapacitor leakage.
• Utilizing an OP27 operational amplifier as an output buffer for low noise performance.

Main Results:

• Achieved output noise levels as low as the equivalent input voltage noise of the OP27 operational amplifier.
• Demonstrated DC accuracy better than 0.05% up to an 8 V output.
• Verified performance through SPICE simulations and prototype measurements.

Conclusions:

• The proposed voltage source design effectively provides a low-noise, high-accuracy biasing solution for low-frequency measurements.
• The developed circuit topology successfully compensates for supercapacitor leakage, enabling high DC accuracy.
• The system's stabilization time is compatible with the long measurement durations required for low-frequency noise analysis.