Patents by Inventor John Edward Sitch

John Edward Sitch 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: 7388535
    Abstract: A sampled-data-integrating front end is employed to convert an optical signal to a digital electrical signal. The front end includes a photodetector and an array of parallel conversion circuits, each including an activation switch, a charge amplifier and an Analog to Digital Converter (“ADC”). The charge amplifier includes a reset switch, a capacitor, and an amplifier. The resent switch is operable to discharge the capacitor. The capacitor is operable to charge to the voltage of a signal charge when the activation switch is closed, and to hold that voltage after the activation switch is opened. The amplifier is operable to provide current at the voltage across the capacitor for a period sufficient to enable the ADC to obtain an accurate sample. The parallel conversion circuits are time-interleaved to provide a selected resolution in the digital electrical representation of the optical signal.
    Type: Grant
    Filed: July 20, 2006
    Date of Patent: June 17, 2008
    Assignee: Nortel Networks Limited
    Inventor: John Edward Sitch
  • Patent number: 5977759
    Abstract: A current mirror circuit comprises first and second resistors for conducting first and second reference currents dependent upon a supply voltage, and first and second current mirrors coupled to the first and second resistors, the second resistor being in series with a voltage reference. The second current mirror mirrors the second reference current, and its mirrored current output is subtracted from the first reference current, the difference current being mirrored by the first current mirror to produce a controlled output current. The circuit can be arranged so that the controlled output current is independent of changes of the supply voltage, or, optionally with further current mirrors and voltage references, so that the controlled output current has a desired relationship with the supply voltage.
    Type: Grant
    Filed: February 25, 1999
    Date of Patent: November 2, 1999
    Assignee: Nortel Networks Corporation
    Inventor: John Edward Sitch