D/a converter capable of producing an analog signal having levels of a

Abstract

In a digital-to-analog converter, a digital input signal of x bits is subjected to digital-to-analog conversion with at least two of x bit positions recognized as a common bit position and converted into analog levels of a number which is different from 2.sup.x where x is an integer. At least one additional common bit position may be selected from the x bit positions except the common bit position. The digital input signal may be pre-processed by the use of a logic circuit prior to the digital-to-analog conversion so as to control the number of analog levels. The digital-to-analog converter is applicable to a modulator which produces a quadrature amplitude modulated signal having a circular arrangement of signal points on a phase plane. A demodulator comprises an analog-to-digital converter for converting the above-mentioned analog signal into a reproduction of the digital input signal.