An active circuit includes (a) a first chopper circuit that receives an input signal and a chopping signal of a frequency higher than a base band of the input signal, and that provides a modulated input signal; (b) an amplifier that receives the modulated input signal and that provides an amplified signal resulting from amplifying the modulated input signal; and (c) a second chopper circuit that receives the amplified signal and the chopping signal to provide an output signal. The chopping signal has a frequency that may be dynamically adjusted to accommodate changes in impedance and signal spectrum as a result of the operations of the chopper circuits. The active circuit further includes a low pass filter that receives the output signal and that attenuates components of the output signal above the base band of the input signal. In this manner 1/f noise introduced by the amplifier is eliminated or reduced.