Design of Chopper-Stabilized Switched-Capacitor Integrator

A low noise fully differential switched-capacitor integrator used in the Σ-Δ modulator was designed by using the chopper stabilization technology. The telescopic cascode structure was adopted in the operational amplifier. Various nonidealities in the switched-capacitor integrator were analyzed in detail. The principle of chopper stabilization was also discussed. Finally, the detailed designs of the operational amplifier, switches and capacitors in the integrator were completed. The Spectre simulation under the Cadence environment indicates that, at a power supply of 3.3 V, the operational amplifier has a unity-gain bandwidth of 110 MHz, an open-loop gain of 76 dB, and the switched-capacitor integrator has an equivalent input noise voltage of 0.2 μV·Hz^-1/2 at 14kHz.