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  Systems and methods for auto gain control in bi-cmos digital to analog convertersUSPTO Application #: 20060087465Title: Systems and methods for auto gain control in bi-cmos digital to analog converters Abstract: The accuracy of output power in a digital-to-analog converter (DAC) is critical in certain applications. When bi-CMOS technology is used to implement a DAC, a number of factors affect the gain accuracy of the DAC. The present invention provides a circuit architecture to reduce the variation in these factors to ensure the accuracy of the output power of a DAC. The architecture comprises a bandgap portion, replica circuit and a DAC. The bandgap portion of the architecture provides a constant voltage, while the replica circuit provide a correct current to drive the DAC. (end of abstract)
Agent: Sterne, Kessler, Goldstein & Fox PLLC - Washington, DC, US Inventor: Chun-Ying Chen USPTO Applicaton #: 20060087465 - Class: 341144000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20060087465. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of priority to U.S. Provisional Patent Application, Application No. 60/620,971, filed Oct. 22, 2004, which is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The invention relates to digital-to-analog converters (DAC), and more particularly to automatic gain control in DACs. [0004] 2. Background Art [0005] A digital-to-analog converter (DAC) is an electronic circuit that receives an n-bit digital word from an interface circuit and generates an analog output that is proportional to the received digital word. Digital codes are typically converted to analog voltages by assigning a voltage weight to each bit in the digital code and then summing the voltage weights of the entire code. [0006] DACs can be designed for a wide range of applications, including general data acquisition applications and special applications, such as, but not limited to, video or graphic outputs, high definition video displays, ultra high-speed signal processing, and digital video recording. [0007] The major factors that determine the performance quality of a DAC are resolution, speed, and linearity. Resolution refers to the smallest change in the output analog signal that is supported. The resolution determines the total number of digital codes, or quantization levels, that will be recognized by a converter. The speed of a DAC is determined by the time it takes to perform the conversion process. Measurement accuracy is specified by a DAC's linearity. Integral linearity, which is also referred to as relative accuracy, is a measure of the linearity over the entire conversion range. It is often defined as the deviation from a straight line drawn between the endpoints and through zero (or offset value) of the conversion range. Differential linearity is the linearity between code transition. [0008] The accuracy of a DAC is critical in certain applications. When a DAC has a high degree of accuracy, the control range of a subsequent gain control loop and complexity of circuit stages that may follow a DAC can be reduced. As a result, system cost and power requirements can be minimized. [0009] When Bi-CMOS technology is used to implement a DAC, at least three factors impact the accuracy of the DAC. First, resistive loads of resistors used in a DAC can vary depending on temperature and fabrication process. Second, the current through differential pairs of transistors within a DAC can vary based on fabrication process, temperature and supply voltage. Third, when bipolar devices are used there is some current flow into the base of the devices due to finite beta (.beta.) values. [0010] What are needed are systems and methods to reduce the impact of the above variations to improve DAC accuracy. BRIEF SUMMARY OF THE INVENTION [0011] The accuracy of output power in a digital-to-analog converter (DAC) is critical in certain applications. When bi-CMOS technology is used to implement a DAC, a number of factors affect the gain accuracy of the DAC. The present invention provides a digital-to-analog auto gain control system to reduce the variation in these factors to ensure the accuracy of the output power of a DAC. The architecture comprises a bandgap portion, replica circuit and a DAC. The bandgap portion of the architecture provides a constant voltage, while the replica circuit provides an appropriate current to drive the DAC. [0012] Further embodiments, features, and advantages of the invention, as well as the structure and operation of the various embodiments of the invention are described in detail below with reference to accompanying drawings. BRIEF DESCRIPTION OF THE FIGURES [0013] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. [0014] FIG. 1 is a diagram of DAC. [0015] FIG. 2 is a diagram illustrating the relationship between base, collector and emitter currents. [0016] FIG. 3 is a diagram of a DAC auto gain control system, according to an embodiment of the invention. [0017] FIG. 4 is a chart showing DAC simulation results with and without beta current compensation, according to an embodiment of the invention. [0018] FIG. 5 provides a method for auto gain control in a digital-to-analog converter, according to an embodiment of the invention. [0019] The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. DETAILED DESCRIPTION OF THE INVENTION Continue reading... Full patent description for Systems and methods for auto gain control in bi-cmos digital to analog converters Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Systems and methods for auto gain control in bi-cmos digital to analog converters patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Systems and methods for auto gain control in bi-cmos digital to analog converters or other areas of interest. ### Previous Patent Application: Digital signal processor optimized for interpolation and decimation Next Patent Application: A/d conversion apparatus Industry Class: Coded data generation or conversion ### FreshPatents.com Support Thank you for viewing the Systems and methods for auto gain control in bi-cmos digital to analog converters patent info. IP-related news and info Results in 1.26486 seconds Other interesting Feshpatents.com categories: Computers: Graphics , I/O , Processors , Dyn. Storage , Static Storage , Printers |
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