A Cryogenic Front-End Preamplifier Operating at 120 K for Bolometric Detector

In this paper, the design and test results of a front-end cryogenic amplifier for a bolometer detector are presented. The amplifier is implemented with two low-noise Si JFETs, where the first FET is configured as a source follower amplifier and the second FET provides a high dynamic resistance to keep the voltage gain very close to unity. A 3 dB bandwidth over a wide range from DC to 10 MHz is achieved in this design. The input voltage noise density is ~ 1.9 nV/√Hz at 300 K, which further reduces to 1.6 nV/√Hz at 120 K. The flicker corner frequency observed is below 50 Hz.