Patents by Inventor Tzu-Ching Chiue

Tzu-Ching Chiue 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).

  • Self-compensated dual tone multiple frequency generator
    Patent number: 5027389
    Abstract: A Dual-Tone Multi-Frequency (DTMF) Generator produces a row and column tone frequency for application to the input of two source follower buffer stages. The outputs of the buffers stages are combined in summation operational amplifier to generate the DTMF Signal. There is a voltage level shift between the input and output terminal of the source followers which can be compensated with a self-compensated circuit. With a perfect match between the compensated signal and the source follower, the operational range of working voltage can be about 1.8V to 5V, and the generator can tolerate threshold voltage variation of the transistors.
    Type: Grant
    Filed: March 8, 1989
    Date of Patent: June 25, 1991
    Assignee: Industrial Technology Research Institute
    Inventors: Tzu-Ching Chiue, Yarn-Chern Chen