Digital-to-analog converter

A digital-to-analog converter comprising:

• a sigma-delta modulator having input means for receiving a digital input signal and operative to generate at its output a 1-bit digital signal modulated synchronously with a clock signal in response to said digital input signal,
• an asynchronous sigma-delta modulator having input means coupled to the output of said sigma-delta modulator to receive said 1-bit synchronously modulated digital signal and being operative in response to the 1-bit synchronously modulated digital signal to generate a bivalent asynchronously modulated signal at its output,
• an analog output filter means, and
• an interface circuit coupled between the output of the asynchronous sigma-delta modulator and an input of the analog output filter means.

In a digital video system, a digital-to-analog converter comprising:

• a sigma-delta modulator having input means for receiving a video frequency digital input signal and operative to generate at its output a 1-bit digital signal modulated synchronously with a clock signal at a frequency that is N times the video frequency in response to said digital input signal,
• an asychronous sigma-delta modulator having input means coupled to the output of said sigma-delta modulator to receive said 1-bit synchronously modulated digital signal and being operative in response to the 1-bit synchronously modulated digital signal to generate a bivalent asynchronously modulated signal at its output,
• an analog output filter means, and
• an interface circuit coupled between the output of the asychronous sigma-delta modulator and an input of the analog output filter means.