PURPOSE: To reduce the total capacitance and the fitting area, by connecting a plurality of varactor diode arrays having a plurality of switches and capacitors in series and determining the capacitance according to the sensitivity of elements at each basic section.

CONSTITUTION: The secondary basic section is formed with switches 1∼10 switched in response to clocks 1, 2, operational amplifiers A1, A2, capacitors C1∼C6 and CA, CB. The capacitors C1∼C6 and the CA, CB are formed with capacitor arrays of variable capacitance having a plurality of switches and capacitors. A plurality of the secondary basic sections are connected in series, and the bit length, i.e., capacity of the basic section is determined in response to the element sensitivity of each basic section.