A 300mV sub-threshold region 2.4GHz voltage-controlled oscillator and frequency divider with transformer technique for ultralow power RF applications

A new ultralow voltage 2.4GHz voltage-controlled oscillator (VCO) and a divide-by-2 frequency divider circuits operating in a CMOS sub-threshold region using a transformer technique have been developed. In the sub-threshold region, the CMOS transistor high frequency performances are decreased to the point where oscillation and frequency division are challenging to achieve. The new proposed VCO uses the transformer feedback complementary VCO technique to improves VCO negative feedback gain. The circuits have been fabricated in a 65 nm standard CMOS process. The oscillation frequency is designed at 2.4 GHz under a 300mV supply voltage. The total power consumption is 202μW with noise performance of %96 dBc/Hz at 1MHz offset. The new proposed frequency divider circuit consists of two stages master-slave D-type flip-flop (DFF). The DFF differential input is coupled to a transformer circuit instead of transistors to reduce the number of stacks. The minimum operating supply voltage is 300mV with power consumption of 34μW with a free-run frequency of 1.085 GHz.