Note: A temperature-stable low-noise transimpedance amplifier for microcurrent measurement.

Area of Science:

• Electronics
• Instrumentation
• Sensor Technology

Background:

• Microcurrent measurements (pA-scale) face a trade-off between low noise and temperature stability.
• High-value resistors, essential for low noise, typically exhibit poor temperature coefficients, limiting instrument accuracy.
• Existing solutions often require complex thermal stabilization, increasing size and cost.

Purpose of the Study:

• To develop a low-noise transimpedance amplifier with superior temperature stability for microcurrent measurements.
• To overcome the inherent limitations of high-value resistors in achieving both low noise and thermal stability.
• To create a compact, self-stabilizing amplifier suitable for demanding applications.

Main Methods:

• Implementation of an active compensation mechanism utilizing a specially designed R-2R compensating network.
• Simultaneous compensation for temperature drifts of feedback resistors, operational amplifiers, and the R-2R network.
• Programmable current gain with fine trimming resolution achieved through the R-2R network.

Main Results:

• Achieved ultra-low-noise performance with an internal current noise density of approximately 0.4 fA/√Hz at a current gain of 10^11 V/A.
• Demonstrated high-temperature stability with an average temperature coefficient of 4.3 ppm/K over the 0-50 °C range.
• The amplifier module maintains accuracy across a wide temperature range without external thermal stabilization.

Conclusions:

• The developed transimpedance amplifier effectively resolves the conflict between low noise and temperature stability in microcurrent measurements.
• The active compensation strategy ensures reliable and accurate measurements in environments with fluctuating temperatures.
• Its compact design and performance characteristics make it ideal for high-precision, low-current sensing in applications like environmental monitoring and bioelectricity detection.