US Patent 10062450 Passive switched capacitor circuit for sampling and amplification

In pipelined analog-to-digital converters (ADCs), a passive switched capacitor (PSWC) circuit can be used in a multiplying analog-to-digital converter (MDAC), which generates an analog output being fed to a subsequent stage. Complementary analog input signals are sampled respectively onto first and second capacitors, which are stacked to provide gain. The first capacitor is positioned between a first input switch and an output node of the PSWC circuit, and the second capacitor is positioned between the second input switch and a digital-to-analog converter (DAC) output. The topology advantageously isolates common modes of the complementary analog input signals, the DAC output, and the output of the PSWC circuit. As a result, the topology offers more degrees of freedom in the overall circuit design when stages having the MDAC are cascaded, resulting in pipelined ADCs with a more elegant design with lower noise and lower power consumption.