Method and apparatus for accurate inverse-linear voltage/current generator

摘要

To make use of its full input voltage operating range, an analog-to-digital converter is configured with a switched-capacitor circuit to produce a digital output signal from an analog input signal that lies within a range of input signal voltage. The analog-to-digital converter is configured with an amplifier with a digitally programmable gain and a voltage generator with a digitally controlled output voltage. The voltage generator is coupled through a buffer to the amplifier input and generates an output voltage inversely proportional to the amplifier gain. The amplifier gain and the voltage generator output voltage are controllable with the same digital control signal. The combination of the amplifier and the voltage generator can be configured to produce a voltage for the analog-to-digital converter that lies in a prescribed voltage range, avoiding the need to generate substantial current from the voltage generator for a switched-capacitor circuit.