Design a combinational circuit with four inputs and four outputs. The output is the 2's complement of the input. Draw the logic diagram Design an Excess-3 error checker. If the input is a valid Excess-3 digit, the output of the circuit is 0. If the input is an invalid Excess-3 digit, the output of the circuit is 1. 2. 3. A sequential circuit has three D flip-flops, A, B, and C, and one input, x. It is described by the following flip-flop input functions DB A DC-B (a) (b) Derive the state table for the circuit. Draw two state diagrams: one for x-0 and one for x-1. 4. A sequential circuit has two JK flip-flops, A and B; two inputs, x and y; and one output, z. The flip-flop functions and the circuit output function are as follows JA-Bx+B'y KA-Bxy KB A+xy (a) Draw the logic diagram of the circuit (b) Tabulate the state table. (c) Derive the next-state equations for A and B (i.e. do K-Maps for NS columns.) 5. Design a sequential circuit with two D flip-flops, A and B, and one input, x. When x-0, the state of the circuit remains the same. Whenx 1, the circuit goes through the state transitions from 00 to 01 to 10 and repeats indefinitely 6. Design a counter that counts in the sequence 0,2,3,6,4. Use T flip-flops Treat the unused states as don't-care conditions. Does the circuit correct itself? Draw the logic diagram