Programmable dynamic range sigma delta A/D converter

A sigma-delta analog-to-digital (A./D) converter, comprising:

• an input circuit having
• a summer that receives and sums oversampled analog input voltage signals and analog reference voltage signals,
• an integrator that integrates said summed signals supplied by said summer,
• an analog-to-digital converter that converts the output of said integrator to digital signals based on an amplitude of said analog reference voltages signals,
• a decimator that receives the digital signals represented by a number of bits supplied by said analog-to-digital converter and supplies an increased number of bits at a rate below the oversampled rate;
• and
• an adjustable reference voltage circuit that selectively provides said analog reference voltage signals, from among a plurality of analog reference voltage signals, to said analog circuit based on the digital signals supplied by the analog-to-digital converter and an amplitude voltage range of said analog input voltage signals over a period of time, wherein the adjustable reference voltages circuit includes an analog multiplexer and gain buffer that supplies a specific reference voltage to shift an operating range, measured by relative input power of the analog input voltage signals, over which said input circuit converts input analog signals to said digital signals.