F UTURE W ORKS

Although the functions of the designed circuits in this thesis are all verified, there are still some subjects and drawbacks could be studied or improved. The first is the design of the two new proposed crystal oscillator circuits could be considered for the crystal operated in overtone region. The second is the new proposed crystal oscillator circuit II needs to be improved to avoid the huge device size of the transistor MP4 to effectively turn off the transistor MP1 in fig. 5.1. The third is the traditional electrostatic discharge (ESD) protection circuits are not suitable for the mixed-voltage applications. Therefore, new ESD protection circuits realized in low-voltage processes must be developed to achieve a good ESD robustness for the mixed-voltage applications. The fourth is the duty cycle of the generated clock signal by a crystal oscillator circuit will vary with process variation, so a simple duty cycle adjustment circuit [29] may need to be studied. Finally, the fabrication of new

proposed crystal oscillator circuit I and II in UMC 130-nm 1.2-V CMOS process is under going, the measurements need to be followed.

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簡歷

[1] Ming-Dou Ker and Hung-Tai Liao “Mixed-voltage crystal oscillator circuit with low-voltage devices,” pending for U.S.A. and R.O.C. Patents.

[2] Ming-Dou Ker and Hung-Tai Liao ”High/Low-voltage-tolerant crystal oscillator circuit realized with only low-voltage devices” pending for U.S.A. and R.O.C.

Patents.

[3] Ming-Dou Ker and Hung-Tai Liao “Design of mixed-voltage crystal oscillator circuit in low-voltage CMOS technology,” to be presented in IEEE Int. Symp. on Circuits and Systems.

[4] Ming-Dou Ker and Hung-Tai Liao “Design of mixed-voltage-tolerant crystal oscillator circuit in low-voltage CMOS technology,” submitted to IEEE Trans.

on Circuits and Systems II.