JPS56110337A - Digital and analog converter - Google Patents

Abstract

PURPOSE:To realize a direct D/A conversion without changing a serial pulse train into a parallel form is case a D/A conversion is given to the serial pulse train, by installing an elastic surface wave device and an analog integrator as the primary component elements. CONSTITUTION:The elastic surface wave device 1 contains the com-bshaped input and output electrodes 5 and 6 on the piezoelectric substrate 3, and the analog integrator integrates the output of the output electrode 6. The input electrode 5 consists of N pairs of normal electrodes (N>=1), and the electrode 6 has a logarithm of 6NXM (M>=2) to be formed into a weighted electrode having a fixed picth of the electrode fingers plus the crossing width of the electrode fingers varying at the rate of 1, 1, 2<i>...2<i> (i=1, 2...M-2) with every N pair and successively at and after the width closest to the input electrode. The means 7 is provided to the integrator 2 to perform a sampling in a state under which the outputs of the output electrode fingers have the same polarity. Then the digital signals are supplied successively from the electrode 5 and through the side of MSB, and thus a D/A- converted output is obtained from the integrator 2.