Design of a Low-Voltage, Low-Power, High-Frequency CMOS Current-Mode VCO Circuit by Using 0.6µm MOS Devices

Yasuhiro SUGIMOTO  Takeshi UENO  Takaaki TSUJI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E80-A   No.2   pp.304-312
Publication Date: 1997/02/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Analog Circuit Techniques for System-on-Chip Integration)
CMOS VCO,  current-mode circuit,  low voltage,  low power,  high-frequency,  

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We have designed a new current-mode low-voltage, low-power, high-frequency CMOS VCO circuit. The main purpose of this new circuit is to obtain operational capabilities with more than 1 GHz oscillation frequency from one battery cell. The current-mode approach was adopted throughout the circuit design to achieve this. New differential-type delay cells in the current-mode operation enable extremely low supply voltage operation and superior linearity between the oscillation frequency and control voltage of a ring oscillator. A design which combines the transitions of each delay cell output enables the VCO's high-frequency operation. To obtain a sufficient current level at output, a current amplifier with a small amount of positive feedback is used. The unnecessary generation of spectral components caused by mismatched time delay of delay cells in a ring-oscillator, which is an inherent problem of the VCO in a ring-oscillator form, is 0also analyzed. The characteristics of the designed VCO were examined by the SPICE circuit simulation using standard CMOS 0.6µm devices. Operation with a 1 V power supply, 1 GHz oscillation frequency, and 5.7 mW power dissipation was verified.