A digitally-controlled oscillator (DCO) includes a current mirror configured to generate a reference current at a first output terminal thereof, and a supply current having a magnitude proportional to a magnitude of the reference current at a second output terminal thereof. An oscillation circuit is provided, which is responsive to the supply current at an input node thereof. This oscillation circuit generates a periodic output signal having a frequency that varies in response to changes in the magnitude of the supply current. A variable resistance circuit is provided, which is responsive to a first control signal having a magnitude that influences a value of a resistance provided between a first node thereof, which receives the reference current, and a second node thereof. A negative feedback circuit is provided, which has first and second current carrying terminals electrically coupled to the first output terminal of the current mirror and the first node of the variable resistance circuit, respectively, and a control terminal electrically coupled to the input node of the oscillation circuit.