100 kHz-1 GHz NMOS variable-frequency oscillator with analog and digital control.

Abstract

According to conventional oscillator design methods, high-speed operation and wideband coverage incompatible specifications are met only separately by tuned or relaxation networks respectively. It is shown that this view is no longer appropriate in the context of fine-line MOS implementations, when suitable circuit techniques are used. A GHz multivibrator with an over-four-decade frequency range for phase-locked loop applications is discussed. In this environment the inherent poor temperature stability of relaxation oscillators is not critical due to the presence of correcting feedback. The fine-line DVCO (digital- and voltage-controlled oscillator) was tested at wafer level with a 3-V power supply and was found operational. The maximum and minimum frequencies for this chip were 1.4 GHz and 800 kHz. Typically, the top speed was 1.1 GHz ±25%, depending on the transistor effective channel length.