D-A CONVERSION CIRCUIT AND ΔΣ AD MODULATOR EMPLOYING IT

Japanese Patent JP3801602

B2

PROBLEM TO BE SOLVED: To provide a D-A converter of a simple arrangement in which nonlinearity can be noise-shaped. SOLUTION: The D-A conversion circuit comprises switches S0-S4 performing the charge, discharge, grounding and polarity reversal of each capacitor in a segment switched capacitor type D-A converter 20, and a controller 10 for controlling the switches S0-S4 to perform the secondary noise shaping of the nonlinearity of the D-A conversion circuit for a low-pass ΔΣ AD modulator by using "+2" operation for obtaining an output voltage equal to +2 times of a reference output voltage by performing charge and discharge twice for each capacitor in a clock period, "+1" operation for obtaining an output voltage equal to 1 time of the reference output voltage by performing charge and discharge once for each capacitor in a clock period, "0" operation for obtaining an output voltage of ground potential without performing charge and discharge, and "-1" operation for obtaining an output voltage equal to -1 time of the reference output voltage by reversing the polarity of each capacity after it is charged once.