Modulator having improved encoding

Abstract

A pulse step modulator includes a plurality of N series connected unit step modules each including a DC voltage source having a value V. A plurality of M series connected binary step modules are connected together in series with the series connected unit step modules with each binary step module including a DC voltage source having a value which is a fraction of V. Each module has an associated actuatable switch means for, when actuated, turning on the associated module to provide a step voltage. An output circuit connected to the series connected modules for providing an output voltage to a load wherein the magnitude of the output voltage is equal to the sum of all of the voltage sources of the modules that are turned on. An analog input signal is converted into digital words, each word including first and second multi-bit digital portions. The first portion is converted into N unit step control signals for controlling actuation of the N unit step modules so that the number of the unit step modules that are turned on is dependent upon the magnitude of the analog input signal. The second multi-bit digital portion includes an M bit binary pattern that varies with increasing and decreasing values of the input analog signal. An encoder responds to the binary bit pattern reaching a preselected binary bit pattern and changes the value thereof by a given amount.