Power supply rejection for pulse width modulated

Abstract : A circuit according to the present invention improves the power supply rejection ratio for a pulse width modulated digital amplifier and can be used as a compressor and/or limiter. The circuit preferably operates by using voltage level translation to vary the amplitude of a triangle wave in response to changes in power supply voltage prior to input of the wave into a comparator of the PWM device. Because the circuit operates to improve power supply rejection, little or no distortion is introduced into the signal when used as a compressor and/or limiter. Additionally, the circuit is optionally implemented in a Class D amplifier, and provides a lower cost of implementation than conventional designs in such implementations.

Claims
What is claimed is:
1. A device for providing improved power supply rejection of a pulse width modulated digital amplifier, comprising:
a buffering mechanism that buffers divided reference voltages;
an oscillator which outputs a first waveform, wherein the first waveform can be combined with the divided reference voltages;
a circuit that performs a voltage level translation, wherein the voltage level translation outputs a second waveform having a similar frequency to the first waveform, wherein the second waveform has an amplitude that varies between the divided reference voltages; and,
an integrator that converts the second waveform into a triangle waveform that can be used with the pulse width modulated digital amplifier.
2. The device of claim 1, wherein the pulse width modulated digital amplifier is a Class D amplifier.
3. The device of claim 1, wherein the buffering mechanism is an operational amplifier.
4. The device of claim 1, wherein the buffering mechanism ensures an accurate low impedance voltage.
5. The device of claim 1, wherein the second waveform is a square waveform.
6. The device of claim 1, wherein the oscillator is a fixed oscillator.
7. The device of claim 1, wherein the first waveform has a 50% duty cycle.
8. The device of claim 1, wherein the divided reference voltages can include ground.
9. A device useful as a compressor or limiter with a Class D amplifier, comprising:
means for rectifying an audio input signal;
means for DC amplifying the audio input signal;
means for injecting the audio input signal into a circuit for providing improved power supply rejection, the circuit comprising:
a buffering mechanism that buffers divided reference voltages;
an oscillator which outputs a first waveform, wherein the first waveform can be combined with the divided reference voltages;
a subcircuit that performs a voltage level translation, wherein the voltage level translation outputs a second waveform having a similar frequency to the first waveform, wherein the second waveform has an amplitude that varies between the divided reference voltages; and,
an integrator that converts the second waveform into a triangle waveform that can be used with the pulse width modulated digital amplifier.
10. A device useful as a compressor or limiter, comprising:
means for rectifying an audio input signal;
means for DC amplifying the audio input signal;
means for injecting the audio input signal into a circuit for providing improved power supply rejection, the circuit comprising:
a buffering mechanism that buffers divided reference voltages;
an oscillator which outputs a first waveform, wherein the first waveform can be combined with the divided reference voltages;
a subcircuit that performs a voltage level translation, wherein the voltage level translation outputs a second waveform having a similar frequency to the first waveform, wherein the second waveform has an amplitude that varies between the divided reference voltages;
an integrator that converts the second waveform into a triangle waveform;
means for inputting pulse-width-modulated signals to a differential amplifier; and
a lowpass filter to restore audio to the output.

Merging Photonics and Electronics at Nanoscale Dimensions Ekmel

Plasmonics: Merging Photonics and Electronics at Nanoscale Dimensions Ekmel Ozbay
Electronic circuits provide us with the ability to control the transport and storage of electrons. However, the performance of electronic circuits is now becoming rather limited when digital information needs to be sent from one point to another. Photonics offers an effective solution to this problem by implementing optical communication systems based on optical fibers and photonic circuits. Unfortunately, the micrometer-scale bulky components of photonics have limited the integration of these components into electronic chips, which are now measured in nanometers. Surface plasmon–based circuits, which merge electronics and photonics at the nanoscale, may offer a solution to this size-compatibility problem. Here we review the current status and future prospects of plasmonics in various applications including plasmonic chips, light generation, and nanolithography.
Nanotechnology Research Center, Bilkent University, Bilkent, Ankara 06800 Turkey

Diagnostic Performance

Diagnostic Performance of Quantitative and Free Light Chain Assays in Clinical Practice Jerry A. Katzmanna, Roshini S. Abraham, Angela Dispenzieri, John A. Lust and Robert A. Kyle
Division of Clinical Biochemistry and Immunology, Department of Laboratory Medicine and Pathology, and Division of Hematology, Department of Internal Medicine, Mayo Clinic College of Medicine, Rochester, MN.
aAddress correspondence to this author at: Department of Laboratory Medicine and Pathology, Hilton 210, Mayo Clinic, Rochester, MN 55905. Fax 507-266-4088; e-mail katzmann@mayo.edu
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Background: The quantitative assay for free light chains (FLCs) is a recently introduced commercial test reported to be sensitive and specific for detecting FLC diseases such as primary systemic amyloidosis (AL), light chain deposition disease (LCDD), nonsecretory multiple myeloma (NSMM), and light chain multiple myeloma. We evaluated its diagnostic performance in clinical practice.
Methods: All FLC clinical test results generated in 2003 were abstracted from the Laboratory Information System. Diagnoses were obtained from the Dysproteinemia database and the patient medical history.
Results: In 2003, we received samples for FLC assays from 1020 Mayo Clinic patients. The majority of these patients (88%) had bone marrow-derived monoclonal plasma cell disorders (PCDs). The 121 patients who did not have monoclonal gammopathy all had FLC / ratios within the range of values obtained for a reference population in our laboratory. Among the patients with monoclonal gammopathies were patients with multiple myeloma (330), AL (269), monoclonal gammopathy of undetermined significance (114), smoldering multiple myeloma (72), plasmacytoma (22), NSMM (20), macroglobulinemia (9), LCDD (7), and a variety of other PCDs. Among the 110 AL patients who had not been previously treated and who had a FLC assay performed within 120 days of diagnosis, the FLC / ratio was positive in 91% compared with 69% for serum immunofixation electrophoresis (IFE) and 83% for urine IFE. The combination of serum IFE and serum FLC assay detected an abnormal result in 99% (109 of 110) of patients with AL

Photonic crystal fibers

Splice-free interfacing of photonic crystal fibers
S. G. Leon-Saval, T. A. Birks, N. Y. Joly, A. K. George, W. J. Wadsworth, G. Kakarantzas, and P. St. J. Russell
Optics Letters, Vol. 30, Issue 13, pp. 1629-1631
Keywords (OCIS):(060.2280) Fiber optics and optical communications : Fiber design and fabrication (060.2310) Fiber optics and optical communications : Fiber optics (230.4000) Optical devices : Microstructure fabrication
AbstractWe report a new method for making low-loss interfaces between conventional single-mode fibers and photonic crystal fibers (PCFs). Adapted from the fabrication of PCF preforms from stacked tubes and rods, this method avoids the need for splicing and is versatile enough to interface to virtually any type of index-guiding silica PCF. We illustrate the method by forming interfaces to two problematic types of PCF, highly nonlinear and multicore. In particular, we believe this to be the first method capable of individually coupling light into and out of all the cores of a fiber with multiple closely spaced cores, without input or output cross talk.

Biomolecular

Tools for the Biomolecular EngineerChristof M. Niemeyer
As traditional "top-down" approaches to device fabrication are reaching their limits, "bottom-up" approaches based on the assembly of individual molecules are receiving increasing attention. Biomolecules such as DNA are particularly promising because of their specific recognition capabilities. In his Perspective, Niemeyer highlights the molecular lithography approach developed by Keren et al. Combined with protein bioengineering, molecular lithography provides a new, powerful tool for using DNA in future nanometer-scale devices.