PURPOSE: To obtain a code converter with a low cost, by controlling a switch which switches the connection between the reference potential and the earth potential to be connected to a capacitor array by means of the code of a signal to be a converted.
CONSTITUTION: In the case of D/A conversion, the connection between the reference potential V and the earth potential is inverted by actuating switches SWA and SWB by a controlsignal given from a decoder circuit 15 that supplies a digital signal. As a result, the position is inverted between a capacitor Cx connected to the reference potential of a capacitor array 3 and a capacitor Cy connected to the earth potential. Thus the analog voltage VOUT of positive and negative signals can be delivered with the control signal given from the decoder circuit 15. For the A/D conversion, the connection between the reference potential and the earth potential is inverted successively in a comparison mode and by actuating switches SWA' and SWB' with the control signal given from a decoder circuit 16. As a result, the position is inverted between the capacitors Cx and Cy. Thus the positive and negative analog input signals are obtained through the same decoder circuit.
GOTOU KUNIHIKO
IWATA ATSUSHI
KIKUCHI HIROYUKI
NIPPON TELEGRAPH & TELEPHONE