A tuning apparatus is provided, wherein the on and off resistances of
semiconductor switches within an tuning IC are optimized, so as to
provide high sensitivity and superior stability, a wide range of tuned
frequency variation, compactness and high performance. The tuning
apparatus has a tuning circuit, which has N-channel MOS transistors (N
transistors) 5a through 5f, serving as a plurality of semiconductor
switches, and a counter circuit 6, which controls the opening and closing
of the N transistors, a plurality of capacitors 4a through 4f, which are
each connected in series with the plurality of N transistors, and a
receiving antenna 2 wherein the total electrostatic capacitance of the
plurality of capacitors is varied by the opening and closing of the
plurality of N transistors, thereby varying the frequency tuned by the
plurality of capacitors and the receiving antenna.