The invention relates to a circuit comprising an amplifier with bipolar transistors, which amplifier is fed by a signal source with a complex internal resistance and which has a signal negative feedback path connecting the amplifier output to the signal source. For reducing the noise, especially the input noise current which is particularly predominant in circuits of this kind which have a sufficiently large source impedance, a reactance network is arranged between the amplifier and the signal source. The network, in connection with the signal source and the negative feedback path, constitutes a filter which is parallel to the amplifier input and which has at least a series resonance frequency within the signal frequency range.