A low phase noise gm-boosted DTMOS VCO design in 180Â nm CMOS technology

This paper presents the design of a low phase noise voltage controlled oscillator (VCO), which offers higher transconductance (gm) by the use of parallel MOSFETs. Here, two NMOS transistors are connected in parallel with the cross-coupled NMOS transistors of a conventional cross-coupled VCO. So, the total negative conductance offered to the circuit to cancel out the parasitic resistance of the LC-tank is increased. This negative conductance is achieved without dealing with larger transistor size or any other passive elements. Hence, power dissipation and silicon area are reduced. Further, dynamic threshold MOSFET (DTMOS) with a capacitive division technique is implemented to increase the voltage swing, leading to a further decrease in phase noise. The proposed VCO is designed and simulated in UMC 180 nm technology. It achieves a tuning range of 1.58-1.60 GHz about 200 MHz, with 6.09 mW power consumption at 1.1 V supply voltage. The phase noise is obtained −40.6 dBc/Hz at 1 kHz and −120.44 dBc/Hz at 1 MHz respectively. So, it should be used in transceiver and PLL blocks for low voltage and low phase noise applications.