DIGITAL-TO-ANALOG CONVERTER

• US 20080117088A1
• Filed: 11/01/2007
• Published: 05/22/2008
• Est. Priority Date: 11/16/2006
• Status: Active Grant

• Current Assignee: Realtek Semiconductor Corp.
• Original Assignee: Realtek Semiconductor Corp.
• Inventors: Huang, Chen-Chih, Wu, Chien-Ming, Lee, Ming-Han
• Granted Patent: US 7,714,756 B2
• Time in Patent Office: Days
• US Class Current: 341/150
• CPC Class Codes: H03M 1/0604 at one point, i.e. by adjusting a single reference value, e.g. bias or gain error gain setting for range control H03M1/18
• CPC Class Codes: H03M 1/742 using current sources as quantisation value generators

Abstract

The present invention discloses a digital-to-analog converter (DAC), including a bias voltage generating unit, a digital-to-analog converting stage, and an operating amplifier. The bias voltage generating unit is utilized for generating a first bias voltage. The digital-to-analog converting stage is utilized for converting a digital signal into a voltage signal, the digital-to-analog converting stage includes a current source for providing a current, and a switching unit is coupled to the current source for controlling the current to pass the switching unit according to the digital signal, and a load. The current flows through the load to generate the voltage signal. The operating amplifier is coupled to the bias voltage generating unit and the digital-to-analog converting stage for controlling the current source according to the first bias voltage.

Claims

1. A digital-to-analog converter, comprising:

a bias voltage generating unit, for generating a first biasing voltage;

a digital-to-analog converting stage, for converting a digital signal into a voltage signal, the digital-to-analog converting stage comprising;

a current source, for generating a current;

a switching unit, coupled to the current source, for controlling the current to pass the switching unit according to the digital signal; and

a load, for outputting the voltage signal when the current flows through the load; and

an operating amplifier, coupled to the bias voltage generating unit and the digital-to-analog converting stage, for controlling the current source according to the first biasing voltage.

2. The digital-to-analog converter of claim 1, wherein the bias voltage generating unit comprises:

a reference current source, for outputting a reference current to generate the first bias voltage;

wherein the current corresponds to the reference current.

3. The digital-to-analog converter of claim 1, wherein an input terminal of the operating amplifier is coupled to the current source of the digital-to-analog converting stage, for adjusting the current.

4. The digital-to-analog converter of claim 1, wherein the current source is an active device.

5. The digital-to-analog converter of claim 4, wherein the active device is a transistor.

6. The digital-to-analog converter of claim 1, wherein the current source is a passive device.

7. The digital-to-analog converter of claim 6, wherein the passive device is a resistor.

8. The digital-to-analog converter of claim 1, further comprising:

a level converting device, coupled between the output terminal of the operating amplifier and the switching unit, for adjusting the voltage level of the digital signal according to the output signal of the operating amplifier.

9. The digital-to-analog converter of claim 8, wherein the level converting device is an inverter or a latch.

10. The digital-to-analog converter of claim 1, wherein the digital-to-analog converting stage further comprises:

a transistor, coupled between the switching unit and the load, for adjusting the current according to the output signal of the operating amplifier.

11. The digital-to-analog converter of claim 10, wherein the transistor is implemented by an I/O fabricating process.

12. The digital-to-analog converter of claim 1, where the digital-to-analog converter is a current steering digital-to-analog converter.

13. A digital-to-analog converter, comprising:

a bias voltage generating unit, for generating a first biasing voltage;

a first current path, for generating a first current according to a control signal;

a digital-to-analog converting stage, for converting a digital signal into a voltage signal, the digital-to-analog converting stage comprising;

a second current path, where a second current flows through the second current path; and

a load, for outputting the voltage signal when the second current flows through the load; and

an operating amplifier, coupled to the bias voltage generating unit, the first current path, and the digital-to-analog converting stage, for outputting the control signal according to the first biasing voltage to adjust the first current and the second current.

14. The digital-to-analog converter of claim 13, wherein the bias voltage generating unit comprises:

a reference current source, for outputting a reference current to generate the first bias voltage;

wherein the first and the second currents correspond to the reference current.

15. The digital-to-analog converter of claim 13, wherein the second current path comprises:

a current source, for generating the second current; and

a switching unit, coupled to the current source, for controlling the second current to pass the switching unit according to the digital signal.

16. The digital-to-analog converter of claim 15, further comprising:

a level converting device, coupled between the operating amplifier and the switching unit, for adjusting the voltage level of the digital signal according to the control signal.

17. The digital-to-analog converter of claim 16, wherein the level converting device is an inverter or a latch.

18. The digital-to-analog converter of claim 15, wherein the current source is a transistor.

19. The digital-to-analog converter of claim 15, wherein the current source is a resistor.

20. The digital-to-analog converter of claim 13, where the digital-to-analog converter is a current steering digital-to-analog converter.