A multiphase
voltage controlled oscillator (e.g., a quadrature VCO) 100, which includes multiple
voltage controllable
transconductance phase drivers 102, 104, 106 and 108. The output of each
voltage controllable
transconductance phase driver 102, 104, 106, 108 supplies one of 4 oscillator phases and receives 2 of the 4 phases as inputs. Each of the voltage controllable
transconductance phase drivers 102, 104, 106 and 108 corresponds to a pair of controllable transconductance inverting amplifiers 132, 134, 136, 138. The controllable transconductance inverting amplifiers may be a simple
inverter 150 that includes N-type FET (NFET) 152 and P-type FET (PFET) 154.
Transconductance is controlled in the simple
inverter by raising or lowering supply voltage (Vdd) levels. A more complex controllable transconductance inverting
amplifier may be used, replacing PFET 154 with series connected PFETs 164, 166. The gate of one PFET 166 is controlled by a bias control voltage VCON. For additional sensitivity and control PFETs 164, 166 may each be replaced with parallel pairs of PFETs 174, 176 and 178, 180. In addition to a quadrature VCO, an N
phase oscillator may be formed with each phase generated by a controllable transconductance functional block, appropriately selecting block inputs from output phases.