A DC coupled signal acquisition system with ultra-wide input range

A signal acquisition system is presented which is suitable for small signals in the presence of low-frequency interference. In a conventional design filters precede the input stage to remove offset and interference. However, filters reduce the available recording bandwidth, are difficult to integrate and remove potentially valuable information about the interference signal and they yield long settling time after disturbance. Instead of removing signal content, the proposed approach extends the available input range. Floating batteries and a simple digital control are used to prevent the input amplifier from saturating. A layout of the system in a 0.35 mum CMOS process is presented and transistor level simulation results are discussed to confirm the operation of the system.