| 摘要 |
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 (L 1 ) 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</SUB>, L 3 or L 4 ) and an inactive semiconductor element (FET 2 , FET 3 or FET 4 ) 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. |
