FEED-FORWARD CIRCUITRY AND CORRESPONDING ERROR CANCELLATION CIRCUIT FOR CASCADED DELTA-SIGMA MODULATOR

摘要

A cascaded delta-sigma modulator includes a first stage delta-sigma modulator having first adder (2) followed by first (3) and second (6) integrators, a second adder (4), and a quantizer (7) the output of which is fed back to the first adder by an A/D (9). A gain circuit (5) is also connected between the first integrator and the second adder. The quantizer output is coupled by interstage circuitry to a second stage converter (100B) having a transfer function represented by the expression OUT(z)=z"nIN(z)+G(z)E2(z). An error cancellation circuit (12) includes inputs coupled to the output of the quantizer and an output of the second stage converter so as to provide a flat transfer function of the cascaded first stage delta-sigma modulator and second stage converter and the error cancellation circuit, despite non-flatness in a transfer function of the first stage delta-sigma modulator.