Digital-to-analog converting circuit

PURPOSE:To obtain a bipolar analog output voltage by a unipolar reference voltage by disconnecting one terminal of a capacitor from a ground at the 2nd potential of the 1st control signal and by grounding one terminal of the capacitor at the 2nd potential of the 2nd control signal. CONSTITUTION:When fresh data is set in a buffer register 127 from an input terminal 132 for a PCM signal while synchronizing with a synchronizing signal, switches 111-118 which correspond to sign bits A2-A4 are set by a control signal 130 from a code converting circuit 128 while a switch 101 is placed at a ground side. Then, the switch 101 is disconnected from the ground and the switches 111-118 are all connected to the side of line l101 by the control signal 130. Thus, an output voltage Vx which has an absolute value equal to and the opposite polarity to an analog voltage value corresponding to the sign bits A2- A4 is developed at the upper electrodes of capacitors 103-110. A sample holding circuit 102 is placed in a sampling state to obtain the analog output voltage at an output terminal 133.