Abstract: A filter applied in a sigma-delta modulator includes an integrator, a signal attenuator and a feedback circuit, in which these components are connected in series sequentially to form a local feedback circuit. The integrator integrates an input signal to output an integral signal. Accordingly, the signal attenuator attenuates the integral signal to output an attenuation signal to the local feedback circuit so as to share a part of attenuation amount to reduce the chip area of the sigma-delta modulator.

Abstract: The invention provides a method of gain error calibration in a pipelined analog-to-digital converter (ADC). In one embodiment, a first stage and a second stage of the pipelined ADC share a common operational amplifier. The first stage is requested to generate the stage output signal thereof according to a first correction number. The second stage is also requested to generate the stage output signal thereof according to a second correction number. A plurality of stage output values generated by stages of the pipelined ADC are collected. The stage output values are respectively correlated with the first correction number and the second correction number to estimate a first gain error estimate of the first stage and a second gain error estimate of the second stage. The first gain error estimate and the second gain error estimate are weighted to obtain a predicted gain error for gain error calibration in the first stage and the second stage.