A radio frequency amplifier, or RF amplifier, is a tuned amplifier that amplifies high-frequency signals used in radio communications. The frequency at which maximum gain occurs in an RF amplifier is made variable by changing the inductance or capacitance of the tuned circuit. An RF amplifier can tune over the desired range of input frequencies. The shunt capacitance permits high gain at radio frequencies because it adversely affects the gain of a resistance-capacitance coupled amplifier. Power gain of RF amplifiers is always limited at high radio frequencies.