Inductance variable device

Abstract

A inductance variable device includes a first inductor, a second inductor magnetically coupled to the first inductor, a current source whose current is variable, electrically connected to the first inductor, and a current control unit. The current control unit controls a current flowing from the current source to the first inductor according to a feedback signal having frequency information in a current flowing in the second inductor to vary a combined inductance of the second inductor.

1 . A inductance variable device comprising: 
 a first inductor;    a second inductor magnetically coupled to the first inductor;    a current source whose current is variable, electrically connected to the first inductor; and    a current control unit which controls a current flowing from the current source to the first inductor according to a feedback signal having frequency information in a current flowing in the second inductor to vary a combined inductance of the second inductor.    
   
   
       2 . The inductance variable device according to  claim 1 , further comprising: 
 a switch provided between the first inductor and the current source, wherein the switch connects the first inductor with the current source or disconnects the first inductor from the current source.    
   
   
       3 . The inductance variable device according to  claim 1 , wherein the first and second inductors are formed in a semiconductor integrated circuit on a semiconductor substrate.  
   
   
       4 . The inductance variable device according to  claim 1 , wherein the first and second inductors are spirally formed of a strip-shaped conductor having one or more spirals.  
   
   
       5 . The inductance variable device according to  claim 1 , wherein the current source is a DC power source.  
   
   
       6 . The inductance variable device according to  claim 5 , wherein the current source can convert a direction of a direct current to be applied to the first inductor.  
   
   
       7 . The inductance variable device according to  claim 1 , wherein the current source is an AC power source.