In one aspect, the decision-making slicer circuit 450 is essentially a highly sensitive latch. The decision-making slicer 450 includes a clocked differential input comparator stage 401, referred to herein as an input stage, comprising transistors 406A-408A and 406B-408B. It produces a differential output at the output nodes QN₉₀ and QP₉₀, depending on whether the differential input voltage V_IP?V_IN is above or below the differential reference voltage V_REFP?V_REFN. In some embodiments, the voltage levels of V_REFP and V_REFN are programmable, thereby allowing to set different thresholds. For a PAM4 system, there would be 3 of such adding slicers 400 to discern the four different voltage levels.

Accordingly, the input stage of the decision-making slicer circuit 450 uses a couple of differential pairs in the input stage having two differential pairs 401 (rather than a single differential pair) connected as a differential comparator structure, so that the input-referred threshold of the latch can be adjusted by setting reference voltages V_REFP and V_REFN. In particular, the latch makes a binary “one” decision when the differential input voltage (V_IP?V_IN) exceeds V_REFP?V_REFN and makes a binary “zero” decision when the differential input voltage (V_IP?V_IN) is below V_REFP?V_REFN. This binary decision appears at the regenerative output nodes (QP₉₀ and QN₉₀) a short time after the latch is activated (by switching CLK₉₀ low). Here the differential comparator structure of the input stage 401 is used to set the threshold to a value between two of the levels of the received PAM4 signal.