A single-ended low pass filter and its double-ended or balanced version
comprising a first coil (Lp1) coupled between a first input (Vin1) and a
first output (Vout1) terminal of the filter, a second coil (Lp2) coupled
between a second input (Vin2) and a second output (Vout2) terminal of
this filter, and a capacitor (C) coupled between the first and second
output terminals. The single-ended or balanced low pass filter further
includes filter enhancement means (FEM) comprising a current sense
circuit (CS) having first inputs coupled across a first impedance
(Rsense1) coupled between the first input terminal and the first coil,
second inputs coupled across a second impedance (Rsense2) coupled between
the second input terminal and the second coil, and an amplifier (A)
having an input coupled to an output of the current sense circuit and
having an output connected to a ground terminal (Vgrd) via a third (Ls1)
and a fourth (Ls2) coils, preferably mounted in parallel and also forming
part of the filter enhancement means. The coils are magnetically coupled
by pairs and are located on a same core of a transformer (T1). This
filter is used in xDSL splitters. The amplifier may comprise the cascade
coupling of a frequency dependent amplifier and a transconductance
amplifier. The coil is then enhanced in value and is made frequency
dependent, giving a multiple order low pass filter.