JPS6439810A - Tracking adjusting circuit in tuning circuit - Google Patents

Abstract

PURPOSE:To correct a variable capacity characteristic, extending over the whole area of a variable range of a channel selection voltage, or partially, by connecting a variable voltage circuit which can be adjusted, to an electrode opposed to an electrode to which a channel selection voltage in a variable capacity diode is applied. CONSTITUTION:When a channel selection voltage Vt is applied to the cathode of a variable capacity diode 2, and it is varied in the increase direction, a variable voltage from a variable voltage circuit 5 connected to an electrode opposed to an electrode to which the channel selection voltage Vt in the variable capacity diode 2 is applied is applied in the increase direction to the anode, as well. That is, the variable voltage applied to the anode of the variable capacity diode 2 becomes a low potential by the lower voltage of the channel selection voltage Vt, becomes a high potential by the higher voltage of the channel selection voltage Vt, and accordingly, the variable capacity of the variable capacity diode 2 is nearly governed by the channel selection voltage Vt applied to the cathode and the capacity to be corrected is small, by the lower voltage of the channel selection voltage Vt, but by the higher voltage of the channel selection voltage Vt, the variable voltage applied to the anode works greatly and the capacity to be corrected becomes large. In such a way, the magnitude of the correction capacity can be set by adjusting the variable voltage circuit 5.