The switching points (KPij) are formed by switching elements )Kij). A chain circuit lies in the output line and consists of a comparator (K) and a storage member in the form of a D-flip-flop, A sample and hold circut contains a memory (C) and a switch (S) and connects one comparator input to the other. The switch's control electrode receives a switching clock signal that defines an initial phase and a switching phase. During each initial phase the momory (C) is recharged to the potenial on the output line (zi) leading to the one comparator input.
