Noise Measurements of a Low-Noise Amplifier in the FDM Readout System for SAFARI

The SPICA-SAFARI instrument requires extremely sensitive transition edge sensor (TES) arrays with a noise equivalent power of \(2 \times 10^{ - 19} \;{\text{W/}}\sqrt {\text{Hz}}\) and a readout system with an output noise that is dominated by the detector noise. It is essential to ensure the frequency domain multiplexing (FDM) readout system in SAFARI meets the noise requirement. The FDM system in SAFARI consists essentially of LC filters, a superconducting quantum interference device, a room-temperature low-noise amplifier (LNA), and a demultiplexer. Here we present a noise study of the LNA from a laboratory amplifier chain. We found the equivalent current and voltage noise of the LNA to be \(5.4\;{\text{pA/}}\sqrt {\text{Hz}}\) and \(315\;{\text{pV/}}\sqrt {\text{Hz}}\), respectively, which are low enough to read out SAFARI’s TES arrays.