Disclosed herein is a signal level conversion circuit for increasing the dynamic range of an Analog-to-Digital Converter. The method uses the N low order bits of M bits together with at least one virtual bit to build several pixel dithering patterns. When switching of the gain occurs, after the gain is switched with the step amplifier not operated and offset is cancelled, the amplifier to which the reception signal is inputted is switched. The MPS provides for both synchronous and asynchronous communication services.