In order to pick up and amplify the desired radio frequency signal, the resistive load in the audio amplifier is replaced by a tuned circuit (also called a parallel resonant circuit)as shown in the figure. The tuned circuit is capable of selecting as particular frequency and rejecting the others.
Thus the use of tuned circuit in the transistor amplifier circuit, makes possible the selection and amplification of a particular desired radio frequency. Such an amplifier is called tuned voltage amplifier. Thus an amplifier, which amplifies a specific frequency (or a narrow band frequencies), is called a tuned voltage amplifier or simply tuned amplifier. It serves following two purposes: (i) Selection of desired radio frequency signal. (ii)Amplification of the selected signal to a suitable voltage level.