Design of very low noise amplifier for high accuracy star tracker in GEO missions

The SNR of the amplifier plays a vital role in achieving the lower volume and mass of a High Accuracy Star Tracker. Poorer SNR can be compensated by larger aperture Optics or by large integration time. Having a larger Optics impose penalty on the overall weight and volume whereas, the large integration time makes system response slower. This calls for the design of low noise amplifier. This paper is about the novel design of a very high performance amplifier for CCD signal readout in High Accuracy Star Tracker application. Unlike the imagers, the Star Tracker has to detect very low intensity star's positions accurately in the field of view. Hence the video-amplifier has to provide low noise floor, in order to achieve high Signal to Noise ratio (SNR). This paper presents a two-stage video amplifier with DC-restoration and fine offset correction dynamically. The amplifier provides a low noise performance of 6e- with a gain of 23 and consumes only of 0.5W power. All the components are selected critically so that the amplifier can be used in both LEO as well as GEO radiation environments.