An active tunable filter circuit for use as an integratable active filter in a mobile radio apparatus, comprises an active amplifier circuit (A) including a reactive feedback network including a first tunable element (L1) set to pass with amplification a wanted input signal, and a passive resonant circuit (P) coupled to the active amplifier circuit and including an inductive element (L.sub.FB, L3 or L4) and an inactive semiconductor element (FET2, FET3 or FET4) having an interelectrode capacitance which in operation resonates with the inductive element at a harmonic of the wanted signal. In one configuration (FIG. 1) the circuit comprises a band pass filter with amplification and in another configuration (FIG. 6-not shown) the circuit comprises a harmonic notch filter with amplification.