Patent ID: 6753801
Filing Date: 2004-06-22
Classification: H03F,H03M

Abstract:
An analog to digital converter comprising:an input stage having an input and including a sample and hold circuit; a plurality of analog to digital stages serially coupled with said input stage and with one another; and a reference voltage circuit adapted to provide a reference voltage to each analog to digital stage of said plurality of analog to digital stages, the reference voltage circuit comprising: a programmable current supply coupled in series with a resistor and an active load between a source of supply potential and a source of ground potential; a differential amplifier having a first differential input and a second differential input, said first differential input coupled through a first capacitor and a switching device to a first terminal of said resistor, said second differential input coupled through a second capacitor and a second switching device to a second terminal of said resistor; a third switching device having a first end coupled to said first capacitor and to said first switching device, and a second end coupled to said second capacitor and to said second switching device; a third capacitor coupled between a first differential output of said differential amplifier and said first differential input; a fourth capacitor coupled between a second differential output of said differential amplifier and said second differential input; a fourth switching device coupled in parallel with said third capacitor and adapted to switchingly bypass said third capacitor; and a fifth switching device coupled in parallel with said fourth capacitor and adapted to switchingly bypass said fourth capacitor.