Patent ID: 8290451

Claim:
A noise reduction circuit comprising: a signal amplifier for amplifying an input signal and outputting an output signal with a supply of power from a power source via a power supply line circuit; and a signal adding circuit for (i) acquiring and attenuating a part of the output signal from the signal amplifier to generate a canceling signal having a phase substantially opposite to a phase of a leakage signal leaking to the power supply line circuit and having an amplitude substantially the same as an amplitude of the leakage signal, and (ii) substantially canceling the leakage signal by adding the canceling signal to the leakage signal, wherein the power supply line circuit comprises: a low-impedance part for substantially shorting a line of the leakage signal with a ground to ground the leakage signal at a frequency of the leakage signal; and a high-impedance part for setting a connection point between the low-impedance part and the signal amplifier to a substantially open-circuited state at the frequency of the leakage signal, and wherein the signal adding circuit adds the canceling signal to the leakage signal at a position which is closer to the power source than the low-impedance part.