An Ultra-Low Drift Amplifier Using a New Type of Series-Shunt MOSFET Chopper

A chopper amplifier of a new type is proposed for the amplification of nanovolt-order dc voltage. The chopper is built by connecting a shunt switch, which is driven at twice the chopper frequency, to the output terminals of a conventional and balanced-type series-shunt MOSFET chopper. The present chopper is free from offset voltage arising from spike voltages and has an input voltage offset temperature coefficient of less than 0.1 nV/°C for a signal source of less than 1 kΩ, and a long-term drift of 2 nV/18 h for signal source resistance of 6.1 Ω.