US 6,114,981 A · D/A converter

Abstract

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.

Claims20

Dependent claims

An over-sampling D/A converter, comprising:

(a) a .SIGMA. .DELTA. modulator for receiving a multibit digital signal to which a DC offset value is added, and outputting a first one-bit digital signal;
(b) a signal generator for receiving the first one-bit digital signal and a clock signal, generating a second digital signal, which is a logical multiplication of the first one-bit digital signal and the clock signal, and a third digital signal, which is a logical addition of the first one-bit digital signal and an inverted signal of the clock signal, and adding the second digital signal to the third digital signal to thus output a fourth digital signal;
and
(c) an analog filter for receiving the fourth digital signal and outputting an analog signal;
wherein the analog filter includes a mute unit which short-circuits a feedback resistor element in a filter amplifier constituting the analog filter and sets a potential of the analog signal as a reference potential of the filter amplifier, and
the reference potential is set substantially equal to an average DC potential of the fourth digital signal.

3 more elements

An over-sampling D/A converter, comprising:

(a) a .SIGMA. .DELTA. modulator for receiving a multibit digital signal to which a DC offset value is added, and outputting a first one-bit digital signal;
(b) a signal generator for receiving the first one-bit digital signal and a clock signal, generating a second digital signal, which is a logical multiplication of the first one-bit digital signal and the clock signal, and a third digital signal, which is a logical addition of the first one-bit digital signal and an inverted signal of the clock signal, and adding the second digital signal to the third digital signal to thus output a fourth digital signal;
and
(c) an analog filter for receiving the fourth digital signal and outputting an analog signal;
wherein the signal generator has a first mute unit which sets the second digital signal to a first potential and the third digital signal to a second potential and fixes the fourth digital signal at a predetermined potential, the predetermined potential being set substantially equal to an average DC potential of the fourth digital signal,
the analog filter includes a second mute unit which short-circuits a feedback resistor element in a filter amplifier constituting the analog filter and sets a potential of the analog signal as a reference potential of the filter amplifier, the reference potential being set substantially equal to the average DC potential of the fourth digital signal.

3 more elements

Dependencies are inferred from the claim text.

D/A converter

Life of this patent

D/A converter

Life of this patent

Abstract

Claims20