Patents by Inventor Francis H. Chan

Francis H. Chan 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: 6025742
    Abstract: A low voltage differential swing driver circuit comprises first and second serially connected field effect transistors connected in series through first and second resistors. Third and fourth field effect transistors are serially connected together through third and fourth resistors. A diode connects one side of each of the serially connected transistors to one side of a source of regulated low voltage. A remaining side of the regulated low voltage source is connected to a remaining side of the serially connected transistors whereby differential currents are produced through the pairs of transistors. A voltage bias source is connected to a junction of said first and second resistors and to the junction of said third and fourth resistors. Control logic supplies a data switching signal to a gate of the first and fourth transistors, and a complementary data switching signal to a gate of said second and third transistors.
    Type: Grant
    Filed: December 31, 1997
    Date of Patent: February 15, 2000
    Assignee: International Business Machines Corporation
    Inventor: Francis H. Chan
  • Patent number: 5969554
    Abstract: A pre-driver circuit in an I/O circuit for an integrated circuit performs the combined functions of voltage level shifting, slew rate control, and tri-state capability, in a single circuit to avoid additional delay caused by implementing any combination of these functions in two or more circuits.
    Type: Grant
    Filed: June 9, 1997
    Date of Patent: October 19, 1999
    Assignee: International Business Machines Corp.
    Inventors: Francis H. Chan, Douglas Willard Stout
  • Patent number: 5719509
    Abstract: A push-pull output driver includes a pair of auxiliary, low current capacity output circuits connected in parallel with a pair of high current capacity, series connected devices. In response to a pulse transition at the input of the driver circuit, one of the high current capacity devices is turned on to provide the current necessary for a change in state of the output signal. After the output signal has reached a steady state level, the associated auxiliary low current capacity device is turned on and the high current capacity device is turned off. For the remainder of the duration of the pulse, the relatively low current required to maintain the output signal is provided by the auxiliary gate. At the next pulse transition, the other of the high current capacity gates is turned on. Since the first high current capacity gate was turned off prior to the pulse transition, only one of the high current capacity devices is drawing current from the supply and the need for a large current supply is eliminated.
    Type: Grant
    Filed: June 5, 1995
    Date of Patent: February 17, 1998
    Assignee: International Business Machines Corporation
    Inventor: Francis H. Chan
  • Patent number: 5486782
    Abstract: A push-pull output driver includes a pair of auxiliary, low current capacity output circuits connected in parallel with a pair of high current capacity, series connected devices. In response to a pulse transition at the input of the driver circuit, one of the high current capacity devices is turned on to provide the current necessary for a change in state of the output signal. After the output signal has reached a steady state level, the associated auxiliary low current capacity device is turned on and the high current capacity device is turned off. For the remainder of the duration of the pulse, the relatively low current required to maintain the output signal is provided by the auxiliary gate. At the next pulse transition, the other of the high current capacity gates is turned on. Since the first high current capacity gate was turned off prior to the pulse transition, only one of the high current capacity devices is drawing current from the supply and the need for a large current supply is eliminated.
    Type: Grant
    Filed: September 27, 1994
    Date of Patent: January 23, 1996
    Assignee: International Business Machines Corporation
    Inventor: Francis H. Chan