Patents by Inventor Andrew H. Crofts

Andrew H. Crofts 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).

  • Precision oscillator circuits and methods with switched capacitor frequency control and frequency-setting resistor
    Patent number: 6614313
    Abstract: A precision oscillator circuit providing a periodic waveform is provided. A periodic waveform is provided by the use of an integrating op-amp circuit in conjunction with a switched capacitor frequency control loop and a user input adapted to be coupled with a frequency-setting resistor. The frequency of the periodic waveform is determined by the values of the switched capacitor and the resistor. The oscillator circuit has an arrangement which minimizes the effect of the op-amp circuit's offset voltage. The user input is kept robust against user-introduced capacitance by the use of controllable current sources and/or controllable voltage sources to bias the op-amp circuit. A linearity correction circuit is also provided to correct for non-ideal op-amp circuits.
    Type: Grant
    Filed: November 21, 2001
    Date of Patent: September 2, 2003
    Assignee: Linear Technology Corporation
    Inventors: Andrew H. Crofts, Michael A. Kultgen
  • Precision oscillator circuits and methods with switched capacitor frequency control and frequency-setting resistor
    Publication number: 20020041217
    Abstract: A precision oscillator circuit providing a periodic waveform is provided. A periodic waveform is provided by the use of an integrating op-amp circuit in conjunction with a switched capacitor frequency control loop and a user input adapted to be coupled with a frequency-setting resistor. The frequency of the periodic waveform is determined by the values of the switched capacitor and the resistor. The oscillator circuit has an arrangement which minimizes the effect of the op-amp circuit's offset voltage. The user input is kept robust against user-introduced capacitance by the use of controllable current sources and/or controllable voltage sources to bias the op-amp circuit. A linearity correction circuit is also provided to correct for non-ideal op-amp circuits.
    Type: Application
    Filed: November 21, 2001
    Publication date: April 11, 2002
    Applicant: Linear Technology Corporation
    Inventors: Andrew H. Crofts, Michael A. Kultgen
  • Precision oscillator circuits and methods with switched capacitor frequency control and frequency-setting resistor
    Patent number: 6342817
    Abstract: A precision oscillator circuit providing a periodic waveform is provided. A periodic waveform is provided by the use of an integrating op-amp circuit in conjunction with a switched capacitor frequency control loop and a user input adapted to be coupled with a frequency-setting resistor. The frequency of the periodic waveform is determined by the values of the switched capacitor and the resistor. The oscillator circuit has an arrangement which minimizes the effect of the op-amp circuit's offset voltage. The user input is kept robust against user-introduced capacitance by the use of controllable current sources to bias the op-amp circuit. A linearity correction circuit is also provided to correct for non-ideal op-amp circuits.
    Type: Grant
    Filed: October 6, 2000
    Date of Patent: January 29, 2002
    Assignee: Linear Technology Corporation
    Inventors: Andrew H. Crofts, Michael A. Kultgen