A wide tuning range voltage-controlled ring oscillator dedicated to ultrasound transmitter

In this paper, a new design for a voltage-controlled ring oscillator (VCO) is presented. Implemented in 0.8 /spl mu/m high-voltage CMOS/DMOS technology provided by DALSA semiconductor with 5 V power supply, this circuit uses relatively devices dimensions and low stages number to operate at low frequency. The new VCO combines three control methods to vary the oscillation frequency. The proposed VCO topology exhibits a very wide tuning range from 13 Hz to 407 MHz with good transient characteristics, which is difficult to get from the conventional VCO. Its power consumption at the maximum oscillation frequency is 29.2 mW.