Patents by Inventor Ansuya P. Bhatt

Ansuya P. Bhatt has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 8705771
    Abstract: Separate control of the operation of an audio amplifier and a charge pump that synthesizes a negative voltage supply (VSS) for improving the dynamic range of the audio amplifier. The audio amplifier is typically powered by a single positive power supply (VDD) and the charge pump is arranged to synthesize a negative voltage supply rail (VSS) that enables a greater dynamic range for the amplifier's “on” and “shut down” modes of operation. Also, when the audio amplifier enters its shut down mode of operation to create at least some isolation from Line_In audio signals provided at the amplifier's output by other electronic devices, the amplifier's charge pump stays “on” and continues to provide the negative voltage supply rail (VSS). In this way, the greater dynamic range offered by the presence of both the positive and negative voltage rails is provided even if the amplifier is in a shut down mode.
    Type: Grant
    Filed: March 30, 2007
    Date of Patent: April 22, 2014
    Assignee: National Semiconductor Corporation
    Inventors: Marcellus R. Chen, Ansuya P. Bhatt
  • Patent number: 8138826
    Abstract: A circuit and method for signal amplification is provided. The circuit includes an amplifier including an input amplifier that is arranged to receive an input analog signal, and to provide an input amplifier output signal by amplifying the input analog signal. The amplifier further includes a DC offset correction circuit that is arranged to determine a DC offset correction for the input amplifier each time the amplifier is powered up. The DC offset correction is performed by iteratively adjusting a DC offset of the input amplifier until the input amplifier output DC offset is zero when the input analog AC signal is zero, within a predetermined tolerance. The DC offset correction circuit is further arranged to provide the determined DC offset correction to the input amplifier during operation of the amplifier.
    Type: Grant
    Filed: July 22, 2010
    Date of Patent: March 20, 2012
    Assignee: National Semiconductor Corporation
    Inventors: Ansuya P. Bhatt, Raminder Jit Singh, Adam Abed, David A. Beeson
  • Patent number: 7898324
    Abstract: An apparatus includes first and second amplifiers, each having an input coupled to an audio signal input and an output coupled to an audio signal output. The second amplifier also has a feedback path from its output to its input. A first switch can be operated to selectively couple and uncouple the audio signal input and the input to the first amplifier to and from a first node. A second switch can be operated to selectively couple and uncouple the input of the second amplifier to and from a second node. A third switch can be operated to selectively couple and uncouple the first node to and from ground.
    Type: Grant
    Filed: March 20, 2009
    Date of Patent: March 1, 2011
    Assignee: National Semiconductor Corporation
    Inventors: Raminder Jit Singh, Ansuya P. Bhatt
  • Patent number: 7714651
    Abstract: A rail-to-rail amplifier is provided. The rail-to-rail amplifier includes a p-type differential pair, an n-type differential pair, switches, and an output stage. The switches are arranged to selectively couple either the p-type differential pair or the n-type differential pair to the output stage so that only one of the differential pairs is coupled to the output stage at a time.
    Type: Grant
    Filed: February 1, 2008
    Date of Patent: May 11, 2010
    Assignee: National Semiconductor Corporation
    Inventors: Sumant Bapat, Ansuya P. Bhatt, Surya Sharma, Gangaikondan Subramani Visweswaran
  • Patent number: 7554408
    Abstract: An audio amplifier with an integrated asymmetric charge pump is provided. The audio amplifier receives VDD and VSS as power supply signals. The integrated charge pump is arranged to provide VSS from VDD, such that VSS is a negative voltage that is lower in magnitude than VDD.
    Type: Grant
    Filed: May 21, 2007
    Date of Patent: June 30, 2009
    Assignee: National Semiconductor Corporation
    Inventors: Huaijin Chen, Marcellus Chen, Ansuya P. Bhatt, Raminder Jit Singh
  • Publication number: 20090115517
    Abstract: A rail-to-rail amplifier is provided. The rail-to-rail amplifier includes a p-type differential pair, an n-type differential pair, switches, and an output stage. The switches are arranged to selectively couple either the p-type differential pair or the n-type differential pair to the output stage so that only one of the differential pairs is coupled to the output stage at a time.
    Type: Application
    Filed: February 1, 2008
    Publication date: May 7, 2009
    Applicant: National Semiconductor Corporation
    Inventors: Sumant Bapat, Ansuya P. Bhatt, Surya Sharma, Gangaikondan Subramani Visweswaran
  • Publication number: 20080290949
    Abstract: An audio amplifier with an integrated asymmetric charge pump is provided. The audio amplifier receives VDD and VSS as power supply signals. The integrated charge pump is arranged to provide VSS from VDD, such that VSS is a negative voltage that is lower in magnitude than VDD.
    Type: Application
    Filed: May 21, 2007
    Publication date: November 27, 2008
    Applicant: National Semiconductor Corporation
    Inventors: Huaijin Chen, Marcellus Chen, Ansuya P. Bhatt, Raminder Jit Singh
  • Patent number: 7227390
    Abstract: A circuit for adaptively adjusting the drive strength of output power transistors in a class D amplifier is provided. The circuit includes a driver circuit and a low-voltage detect circuit. The low-voltage detect circuit is arranged to assert a low-voltage detect signal if a low supply voltage condition is detected. The driver circuit is arranged to increase the drive strength if the low-voltage detect signal is asserted. The driver circuit includes a first driver and a second driver. The second driver is enabled if the low-voltage detect signal is asserted, and disabled if the low-voltage detect signal is unasserted.
    Type: Grant
    Filed: January 25, 2005
    Date of Patent: June 5, 2007
    Assignee: National Semiconductor Corporation
    Inventors: Sumant Bapat, Ansuya P. Bhatt
  • Patent number: 7170340
    Abstract: A class D power amplifier is provided to drive a low impedance load for audio applications. The amplifier includes a sigma-delta modulator circuit including three or more integrators that are arranged for third or higher order sigma-delta modulation. Also, the sigma-delta modulator circuit includes a quantizer circuit that is arranged to provide a sigma-delta modulator output signal based on a three-level switching scheme. The class D power amplifier drives a speaker based on the three-level switching scheme so that the output switches between three levels: VDD, 0, and ?VDD, based on the input signal.
    Type: Grant
    Filed: January 25, 2005
    Date of Patent: January 30, 2007
    Assignee: National Semiconductor Corporation
    Inventors: Ansuya P. Bhatt, Sumant Bapat
  • Patent number: 7170266
    Abstract: A fully differential class D amplifier includes a pulse width modulator and a power stage. The pulse width modulator is arranged to employ a differential output signal provided from the power stage as a feedback signal. The pulse width modulator includes a transimpedance amplifier that is arranged to generate a triangle wave from the input signal and the feedback signal. The transimpedance amplifier is arranged to generate the triangle wave such that the triangle wave that has approximately a 50% duty cycle when no input signal is applied. Additionally, the input signal adjusts the frequency of the triangle wave such that the triangle wave is a spread spectrum signal. The triangle wave is compared to a threshold signal to provide a pulse width modulated signal.
    Type: Grant
    Filed: June 18, 2004
    Date of Patent: January 30, 2007
    Assignee: National Semiconductor Corporation
    Inventors: Kazim Seven, Ansuya P. Bhatt
  • Patent number: 7164312
    Abstract: A circuit for audio amplification includes an amplifier and a first input resistor. The amplifier is arranged to provide an amplifier output signal that is based, in part, on a capacitively-coupled audio input signal. The capacitively-coupled audio input signal is based, in part, on an input RC value. The input RC value is given by the input capacitance times the input resistance. The input resistance is reduced during the turn-on in order to achieve a fast turn-on time with minimal pop-and-click noise. Also, the input resistance is increased to its normal value after the turn-on so that full audio fidelity is substantially maintained during normal operation.
    Type: Grant
    Filed: August 2, 2004
    Date of Patent: January 16, 2007
    Assignee: National Semiconductor Corporation
    Inventors: Raminder Jit Singh, Ansuya P. Bhatt
  • Patent number: 5475336
    Abstract: A small and easy to fabricate programmable current source correction circuit. The correction circuit consists of a first current division circuit for establishing a reference current; a programmable correction current circuit for establishing the amount of correction current required; a second current division circuit for further reducing the reference current into smaller step or resolution; and a source-sink controlling circuit for determining whether the present invention is to operate as a current sink or current source. The present invention consists of substantially less number of circuit modules and can be fully integrated into a single chip which requires substantially smaller chip area and can operates at a substantially higher frequency compared to prior art.
    Type: Grant
    Filed: December 19, 1994
    Date of Patent: December 12, 1995
    Assignee: Institute of Microelectronics, National University of Singapore
    Inventors: Raminder J. Singh, Ansuya P. Bhatt, Khen S. Tan
  • Patent number: 4576887
    Abstract: Photoconductive organic polymers useful in the preparation of photodetectors and photoconductive devices comprise a transrich polyphenylacetylene. The photoconductive properties may be further enhanced by the addition of an electron-acceptor dopant, and sensitized to selected spectral regions by the addition of a selected dye.
    Type: Grant
    Filed: November 14, 1983
    Date of Patent: March 18, 1986
    Assignee: The Research Foundation of State University of New York
    Inventors: Paul Ehrlich, Wayne A. Anderson, En T. Kang, Ansuya P. Bhatt