Coded data generation or conversion – Analog to or from digital conversion – Nonlinear
Reexamination Certificate
1999-05-07
2001-03-27
Young, Brian (Department: 2819)
Coded data generation or conversion
Analog to or from digital conversion
Nonlinear
Reexamination Certificate
active
06208278
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to electronic circuits. In particular, the present invention relates to digital to analog conversion for electric circuits.
RELATED APPLICATIONS
The present invention is related to a concurrently filed patent application, entitled SYSTEM AND METHOD FOR EXPONENTIAL DIGITAL TO ANALOG CONVERSION.
BACKGROUND OF THE INVENTION
Digital to analog conversion is a process in which signals having a few (typically two) defined levels or states are converted into signals having quantized analog states. The number of quantization states is typically equal to two to the power of digitized input bits. For example, if there are four digitized input bits, then there will typically be 2
4
different quantized analog states. A digital signal typically has two states: zero and one. Analog signals theoretically have infinite number of states and conveys data as electronic signals of varying frequency or amplitude that may be added to carrier waives of a given frequency. An example of a digital to analog conversion is the processing by a modem of computer data into audio frequency tones that can be transmitted over a telephone line. The circuit that performs this function is typically referred to as a digital to analog converter (DAC). Binary digital impulses typically appear as long strings of ones and zeros that typically have no apparent meaning to a human observer. However, when a DAC is used to decode the binary digital signals, meaningful output can appear. Examples of these outputs include voice, picture, musical tone or mechanical motion.
The transfer characteristics of DACs are typically linear. However, there may be some applications that require nonlinear transfer characteristics. For example, it may be desirable to compress data when a signal is large and not compress data in the remaining signal.
It would be desirable to have an integrated circuit that provides nonlinear transfer characteristics of a DAC. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention relates to digital to analog conversion. According to an embodiment of the present invention, a logarithmic transfer characteristic may be produced by subtracting a fraction of the output current from a reference current in a recursive equation.
A system for a digital to analog conversion according to an embodiment of the present invention is presented. The system comprises a digital to analog conversion circuit, and a node coupled to the digital to analog conversion circuit, wherein a fraction of an output current is subtracted from a reference current at the node.
A method for a digital to analog conversion according to an embodiment of the present invention is also presented. The method comprises providing a reference current; providing an output current; and subtracting a fraction of the output current from the reference current.
REFERENCES:
patent: 4558242 (1985-12-01), Tuthill et al.
patent: 4590456 (1986-05-01), Burton et al.
patent: 5258757 (1993-11-01), Reynolds
patent: 5757298 (1998-05-01), Manley et al.
patent: 5841384 (1998-11-01), Herman et al.
Infineon Technologies North America Corp.
Young Brian
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