Linearity in a quantized feedback loop

An apparatus, comprising:

• a first adder configured to receive an input signal and a feedback signal and to output a sum of the input signal and the feedback signal as an error signal;
• a filter coupled to the first adder and configured to receive as an input the error signal, generate a filtered error signal, and output the filtered error signal;
• a quantizer coupled to the filter and configured to receive as an input the filtered error signal and to generate a plurality of quantizer outputs upon receipt of a series of clock signals, each one of the plurality of quantizer outputs being high or low depending upon the filtered error signal;
• a control circuit configured to generate a plurality of control signals, each one of the plurality of control signals selecting a different one of a plurality of multi-bit feedback signals comprising a plurality of quantizer outputs;
• and
• a switch coupled to the control circuit, the quantizer, and the first adder, the switch having a first position in which a first one of the plurality of control signals selects a first one of the multi-bit feedback symbols to be fed back to the first adder and a second position in which a second one of the plurality of control signals selects a second one of the multi-bit feedback symbols to be fed back to the first adder;
• whereby the first adder receives as the feedback signal either the first one of the plurality of multi-bit feedback symbols or the second one of the plurality of multi-bit feedback symbols to be added to the input signal.