Analog-digital converter

Claim 1

An analog-digital converting system comprising: an input for an analog waveform; a reference voltage generator which generates A reference sine-wave voltage having stable amplitude and stable frequency, said frequency defining the repeated instants of conversion; modifying means for modifying said amplitude of said reference sine-wave voltage in selected amplitude steps; a variable gain amplifier arranged to receive both said analogue input and modified reference sine wave voltage and to provide at its output these two signals amplified in the same manner; filtering means for separating the amplified analog input voltage from the amplified modified reference sine wave voltage, respectively; said amplified analog input voltage controlling the gain of said variable gain amplifier; means for providing, from the peak values of said amplified modified reference sine wave voltage, repetitive constant reference voltages, which are related to said peak values; an elementary converter arranged to receive the separated amplified analog input voltage and said repetitive constant reference voltage to convert said separated amplified analog input voltage into an output digital signal; control means arranged to actuate said modifying means should said output digital signal tend to be outside a predetermined range, whereby said input analog waveform may be converted into said output digital signal in a substantially wider conversion range than the conversion range of said elementary converter.