A current re-use PA-VCO cell for low-power BLE transmitters

A current re-use PA-VCO cell for FSK transmitters is presented. High efficiency and low phase noise are obtained through the stacking of a PA and a class-C VCO. Without the use of any DC-DC converters, the voltage headroom of these two blocks can be set maximizing the efficiency of both the PA and the VCO. The structure is inserted in a 130nm CMOS BLE transmitter. A TX efficiency of 17.5% is achieved delivering an output power of -1dBm at 2.4GHz with a VCO phase noise of -129dBc/Hz @ 2.5MHz frequency offset.