Coded data generation or conversion – Analog to or from digital conversion – Differential encoder and/or decoder
Reexamination Certificate
2001-03-30
2002-08-27
Tokar, Michael (Department: 2819)
Coded data generation or conversion
Analog to or from digital conversion
Differential encoder and/or decoder
C341S144000, C341S136000, C341S118000, C341S119000
Reexamination Certificate
active
06441760
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates in general to electronic circuits and, more particularly, to digital to analog converters.
2. Description of the Related Art
Digital-to-analog converters (DACs) are used in many applications where data is processed in the digital domain and converted to the analog domain. A typical example of DAC use is in cellular telephones, where voice data is communicated digitally and converted to an analog signal to drive a speaker for output to the user. DACs are used in a wide range of applications in many different devices.
In many applications, minimizing the consumption of power is extremely important since the device is powered by a battery. For portable devices such as cellular phones and portable audio equipment, a major selling factor is the size and weight of the device. Accordingly, the size, and hence the capacity, of the battery used to power the device is diminishing, while the appeal of longer battery life and output quality are increasing.
Therefore, it is beneficial to use a highly efficient class-D amplifier stage in a DAC. Unfortunately, the modulation of the class-D amplifier stage by a pulse width modulation device (PWM) results in common mode noise generation. To compensate for the common mode noise, the prior art uses a feedback control system that requires conversion of the analog output of the class-D amplifier to a digital signal to be used in the PWM. This feedback system complicates the design and increases power requirements.
Therefore, a need has arisen for a more efficient digital to analog converter, without sacrificing output quality.
BRIEF SUMMARY OF THE INVENTION
In the present invention, a digital to analog converter comprises an amplifier circuit and a pulse width modulator. The pulse width modulator generates signals on first and second nodes of amplifier circuit to create a differential signal. Compensation circuitry generates an identical signal on said first and second nodes to obtain a desired common mode average signal between said first and second nodes, such that said differential signal is not affected.
The present invention provides significant advantages over the prior art. First, the analog/ digital converter is no longer needed, because feedback is not necessary for the compensation. Thus, the circuit design is simplified and the power consumed by the analog/digital converter is eliminated. Second, the compensation signals do not affect the differential signal, resulting in a pure signal.
REFERENCES:
patent: 4079373 (1978-03-01), Brown
patent: 4978959 (1990-12-01), Chong et al.
patent: 5010337 (1991-04-01), Hisano et al.
patent: 5369402 (1994-11-01), Kwon
patent: 5608401 (1997-03-01), Viswanathan et al.
patent: 5614903 (1997-03-01), Oyama
Albinet Xavier
Guigon Pascal
Brady III W. James
Hernandez Pedro P.
Mai Lam T.
Tokar Michael
LandOfFree
Method and apparatus for digital to analog conversion does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for digital to analog conversion, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for digital to analog conversion will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2961913