A/D CONVERTER HAVING TEST CIRCUIT

PURPOSE:To test a comparator of the A/D converter at a high speed by providing a test equipment onto a semiconductor chip for an integrated A/ D converter. CONSTITUTION:A reference voltage is fed to input terminals VT, VB and a specified reference voltage VR is given to comparators 10 by various steps of a resistance ladder. An analog input is fed to the plural comparators 10 from an input terminal VX. The comparator is tested by giving a variable voltage source having a step from a minimum limit accepted on the production till a highest limit to a signal input terminal. Only a comparator generating an output (1) turns on one of FETs in parallel with a NOR gate 70 in the recognition of VX>=VR to be contributed to a current at an output 74. Only a comparator generating an output (0) in the recognition of VX