Transformer-based low frequency noise measurement system for the investigation of infrared detectors’ noise

The paper presents a noise measurement system particularly suited for the investigation of the low frequency noise in advanced infrared (IR) detectors characterized by low shunt resistance. By combining the performances of ultra-low noise amplifiers with the advantages that can be obtained by transformer input coupling and cross-correlation between two nominally identical channels, we were able to obtain excellent noise performances in the low frequency region (below 10 Hz). Indeed, the equivalent input background noise that can be obtained with the approach we propose can be as low as 1 × 10-20 V2/Hz (≈100 pV/√Hz) at 1 Hz. The system was tested using source resistances in the range from 1 to 10 Ω as well as actual advanced IR detectors to demonstrate its ability to provide information about the noise generated at very low frequencies.