Patents by Inventor Christina P. Q. Phan

Christina P. Q. Phan 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: 5202645
    Abstract: Operational amplifiers are often used in unity gain configurations where the output is fed back to the input. In the noninverting buffer configuration the output is directly connected to the inverting input and the circuit becomes a voltage follower. In many cases, the input stage includes cascode coupled transistors which isolate the current mirror load from the differentially operated input transistors. Such cascode transistors act to increase gain to reduce noise and to increase the power supply rejection ratio. When cascode coupled transistors are employed the frequency compensation capacitor can be isolated from loading effects on the input stage, thus, further enhancing the value of a cascoded input stage. However, when such an operational amplifier is operated as a unity gain device its transient response can suffer. Negative output transitions can result in circuit ringing following the negative output transient steps.
    Type: Grant
    Filed: December 12, 1991
    Date of Patent: April 13, 1993
    Assignee: National Semiconductor Corporation
    Inventors: Christina P. Q. Phan, James B. Wieser