Floating-point A/D and D/A converter

An apparatus for producing digital signals indicative of a floating decimal point representation of widely ranging input analog signals in a delta modulation servo loop comprising:

• a serially connected resistor coupled to receive the input analog signals for assuring that the input analog signal is an input analog current signal;
• an operational amplifier having a resistive feedback loop to produce a positive voltage and negative voltage coupled to the serially connected resistor for comparing the analog current signal with a derived reference signal to produce the negative voltage if the analog current signal exceeds the derived reference signal and the positive voltage if the analog current signal is less than the derived reference signal, the derived reference current is subtracted from the input signal current therefore resulting in small currents and voltages for the system to operate on;
• an inverter circuit coupled to the operational amplifier for generating a logic signal representative of a positive voltage and a logic signal representative of a negative voltage;
• an interconnected floating point processing unit and microprocessor coupled to the inverter circuit for providing a first group of digital signals indicative of the mantissa and a second group of digital signals indicative of the order of magnitude;
• a first high speed multiplying digital-to-analog converter coupled to a reference potential source and coupled to the interconnected floating point processing unit and microprocessor for converting the first group of mantissa digital signals to a mantissa component of the derived reference signal;
• a second high speed multiplying digital-to-analog converter coupled to a reference potential source and coupled to the interconnected floating point processing unit and microprocessor for converting the second group of order of magnitude digital signals to an order of magnitude component of the derived reference signal, the first high speed multiplying digital-to-analog converter is coupled to receive the voltage signals derived from the second high speed multiplying digital-to-analog converter and the second high speed multiplying digital-to-analog converter is coupled to a reference source of voltage;
• means coupled to the first and second high speed multiplying digital-to-analog converters for multiplying the mantissa component and the order of magnitude component into the derived reference signal and for feeding the derived reference signal and input analog current signal to the comparing means;
• means coupled to receive the first and second groups of digital signals for passing them to user components;
• means for feeding in a current signal to the operational amplifier when the widely ranging input analog signals are current signals;
• and
• means for amplifying and inverting the derived reference current coupled between the outputs of the first and second high speed multiplying digital-to-analog converters and operational amplifier.