Analysis of thermal noise and the effect of parasitics in the charge-pump integrator

The concept of using capacitive charge-pumps to reduce the power consumption in switched-capacitor (SC) integrators is further extended. It is shown that the charge-pump (CP) integrator can be implemented using both opamp-based and comparator-based SC circuits and achieve significant power savings. When the input sampling capacitor is split into two capacitors, the opamp-based CP integrator ideally consumes 1/4 of the power of a conventional SC integrator, while maintaining almost the same thermal noise performance. An analytical expression for the input-referred thermal noise of the CP integrator is derived and compared with the conventional integrator. The effect of parasitic capacitances on the CP integrator circuit is discussed. Input-referred thermal noise simulation results are provided.