Abstract: An analog-digital conversion system includes an analog-digital converter; and a preamplifier circuit which is provided in the previous stage of the analog-digital converter and differentially amplifies an input analog signal. In the preamplifier circuit, an offset voltage and/or a noise occurs and/or is mixed. The preamplifier circuit outputs two types of analog amplified differential signals where a phase is inverted only with respect to the offset voltage and/or the noise. The analog-digital converter has an averaging circuit which averages the two types of analog amplified differential signals for each clock cycle of sampling preceding an analog-digital conversion and outputs a digital signal based on the differential signal averaged by the averaging circuit.

Abstract: The present invention provides a system for testing a memory array and corresponding support circuitry. The present invention provides a highly efficient testing mode to be entered that allows any type of advanced testing to be performed on the memory array without regard to the restrictions imposed by the various status flags that may be present. The testing mode can be entered by a completely user-defined mechanism. During this testing mode, the user has complete control over the contents of the memory array and can also have complete control over the positioning of the write word line with respect to the read word line without, for example, any write-read word line pointer equality signals being generated. In one example of the present invention used in a FIFO, testing times required for data retention testing are reduced from approximately six seconds to approximately 500.mu.