2008 Volume E91.A Issue 2 Pages 504-512
A design of a low-power CMOS ring oscillator for an application to a 13.56MHz clock generator in an implantable RFID tag is proposed. The circuit is based on a novel voltage inverter, which is an improved version of the conventional current-source loaded inverter. The proposed circuit enables low-power operation and low sensitivity of the oscillation frequency, fOSC, to decay of the power supply VDD. By employing a gm-boosting subcircuit, power dissipation is decreased to 49μW at fOSC=13.56MHz. The sensitivity of fOSC to VDD is reduced to -0.02 at fOSC=13.56MHz thanks to the use of composite high-impedance current sources.