| 摘要 |
A feedback topology delta-sigma modulator having an AC-coupled feedback path reduces signal level in the loop filter, easing linearity requirements and reduces capacitor size requirements for the filter integration stages. The delta-sigma modulator includes a loop filter having multiple integrator stages, a quantizer, and a feedback network providing at least two feedback paths to corresponding integrators in the loop filter. In one aspect, only one of the feedback paths from the quantizer output is DC coupled, and at least one other of the feedback paths is DC-coupled, which reduces the signal levels in the loop filter integrators. In another aspect, at least one of the feedback paths from the quantizer is AC coupled, providing a similar result. The AC feedback path may be provided through a series-connected resistor and capacitor. The DC feedback path may be provided through a resistor, a switched-capacitor network, or may be a quantizer-controlled current source. |
