CMOS Current-controlled Oscillators

The work presented in this paper is about the design of current-controlled oscillators (ICO). Two ICOs are proposed. Aiming at reducing the duration of the short-circuit currents caused by slowly-changing voltages in the circuits, signal conversion blocks are introduced to generate sharp pulses. In this way, the power efficiency of the circuits is improved, which leads to an extensive performance improvement of the circuits. Both ICOs can operate over a frequency range from 100 KHz to 900 MHz. The quality of the output waveforms before buffers is good and over the entire frequency range the rise/fall time is consistently short. The power dissipation of the ICOs is very low, the same as that of a 5-stage current-starving ring oscillator. Moreover, the scheme of the ICOs allows an easy adjustment of the duty cycle of the output pulse signals. A simple digital control structure of the duty cycle has also been proposed.