Patents by Inventor Craig E. Johnston

Craig E. Johnston 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).

  • Auto-zero amplifier circuit with wide dynamic range
    Patent number: 4276513
    Abstract: An operational amplifier (33) is continuously switched back-and-forth between an auto-zero mode of operation and an accurate amplification mode of operation. During the auto-zero mode of operation, the junction between an offset voltage compensation (e.g., auto-zero) capacitor (35) and the noninverting input of the operational amplifier (33) is referenced to the input signal voltage via a bootstrap amplifier (31), rather than being tied to ground. Further, during the auto-zero mode of operation, the other end of the auto-zero capacitor (35) is referenced to the output of the operational amplifier (33), which is also connected to the inverting input of the operational amplifier. As a result, the auto-zero capacitor (35) is charged to a voltage level equal to the input offset voltage of the operational amplifier, but in polarity opposition thereto.
    Type: Grant
    Filed: September 14, 1979
    Date of Patent: June 30, 1981
    Assignee: John Fluke Mfg. Co., Inc.
    Inventors: Craig E. Johnston, Ramesh C. Goyal