A chopper-stabilized high-pass DeltaSigma Modulator with reduced chopper charge injection
In this paper, a chopper-stabilized high-pass DeltaSigma Modulator (DSM) is reported with experimental results. A new circuit technique to suppress the residual offset caused by the chopper switch charge injection is proposed. Enabled by an amplifier sharing architecture, the technique diverts the error charge generated by the critical chopper to the second stage of the modulator such that the resulted error becomes first-order high-pass shaped. Fabricated in a 0.18?m CMOS technology, the 2nd-order DSM realizes 82dB dynamic range over a 1kHz bandwidth while consuming 144?W from a 1.8V supply. The offset is 403?V and the flicker noise is invisible in the measured output spectrum down to 4Hz. The core area of the chip is 0.16mm2.
high-pass deltasigma modulator amplifier sharing chopper stabilization