Comments on "Efficient Multibit Quantization in Continuous-Time $\Sigma \Delta$ Modulators

The authors propose three different types of continuous-time modulators to reduce the number of comparators in the main quantizer. Employing an auxiliary quantizer helps to reduce the integrator swing range in front of the main quantizer and to decrease the number of comparators. We wish to remind that the use of the auxiliary quantizer to minimize the number of comparators was published earlier and further implemented in silicon