公开(公告)号：EP0889589A3

公开(公告)日：2001-01-31

申请号：EP98301197.4

申请日：1998-02-18

申请人： FUJITSU LIMITED

发明人： Ozawa, Naoki, c/o Fujitsu Limited ,  Tani, Hiroaki, c/o Fujitsu LSI Technology Limited ,  Nomura, Kenichi c/o Fujitsu LSI Technology Limited

IPC分类号： H03K3/03

CPC分类号： H03K3/0315 ,  H03K3/014

摘要： A voltage controlled oscillation circuit with an oscillation frequency thereof controlled in accordance with an external voltage is disclosed. An odd number of inversion circuit elements (1-1 to 1-(2n+1)) such as inverters for inverting output signals thereof with respect to input signals thereto are connected in series with each other. An output side of the last-stage one of the odd number of the inversion circuit elements (1-1 to 1-(2n+1)) is connected to an input side of the first-stage one of the inversion circuit elements (1-1 to 1-(2n+1)) to thereby cause an oscillation. A plurality of oscillation frequency variable control units (2-1 to 2-(2n+1)) such as variable resistor circuit elements for changing an oscillation frequency in accordance with an external voltage are each inserted between each set of adjacent inversion circuit elements. A plurality of fixed resistor circuit elements (3-1 to 3-(2n+1)) each having a fixed resistance value are connected in parallel with a plurality of the oscillation frequency variable control units (2-1 to 2-(2n+1)), respectively. The functions of both the variable resistor circuit elements and the fixed resistor circuit elements can be carried out at the same time by the use of a depletion type transistor or a transistor of a short channel type.