An operating parameter method and circuitry are provided that generate operating parameter signals that are compensated for noise. Such operating parameter circuitry includes control loop circuitry that operates from a first power supply to provide an operating parameter signal to functional circuitry operating from a second power supply separate from the first power supply. The control loop circuitry comprises generator circuitry to generate the operating parameter signal based on an input signal. Replica generator circuitry operates from the second power supply to generate a further operating parameter signal based on the input signal. Adjustment circuitry performs a comparison on the operating parameter signal and the further operating parameter signal and causes an adjusted input signal to be produced in dependence on a result of the comparison. The adjusted input signal is received by the generator circuitry. Consequently, the generator circuitry is able to produce an operating parameter signal that has been compensated for noise in the circuit.