There is provided an over-sampling D / A converter which has a mute function for fixing an average
DC potential of an analog output
signal to a predetermined potential, and comprises a SIGMA
DELTA modulator for receiving a multibit
digital signal to which a DC offset value is added and then outputting a one-bit non-return-to-zero
signal, a
signal generator for receiving the non-return-to-zero signal and the
clock signal, then generating a return-to-zero signal which is a logical multiplication of the non-return-to-zero signal and the
clock signal and a complementary signal of the return-to-zero signal which is a logical addition of the non-return-to-zero signal and an inverted signal of the
clock signal, and then adding the return-to-zero signal to the complementary signal of the return-to-zero signal to thus output a polar-return-to-zero signal, and an analog filter for receiving the polar-return-to-zero signal and then outputting an
analog signal. Accordingly, because an average
DC potential of an output signal at the time of the mute operation-ON is set substantially equal to the average
DC potential of the output signal at the time of the mute operation-OFF, variation in the average DC potential in the output signal due to ON / OFF of the mute operation can be prevented. As a result, generation of audible click noises can be prevented.