An enhanced negative resistance voltage controlled oscillator (VCO) circuit is provided, in which a parallel connection of a capacitor and a resistor configured to provide frequency-dependent transconductance is present across source nodes of a first pair of field effect transistors in which gate nodes and drain nodes are cross-coupled. The source nodes of the first pair of field effect transistors are electrically shorted to drain nodes of a second pair of field effect transistors of which the gate nodes are electrically shorted to the gate nodes of the first pair of field effect transistors. The parallel connection of the capacitor and the resistor includes a parallel connection of a capacitor and a resistor such that the net transconductance of the first pair of field effect transistors is less at low frequencies where thermal noise and flicker noise are dominant part of the phase noise than at the operational frequency range.