| 摘要 |
<P>PROBLEM TO BE SOLVED: To adjust impedance with sufficient precision. <P>SOLUTION: An impedance adjusting circuit includes: terminals 13, 14 connecting the other ends of resistances 11, 12 whose one ends connected to a power source Vdd; a variable resistance element 19 whose one end is connected to the terminal 13 via a switch element 17 and the other end is grounded; and a variable resistance element 20 whose one end is connected to the terminal 14 via a switch element 18 and the other end is connected to one end of the variable resistance element 19. The switch element 17 is turned on and the switch element 18 is turned off. Then, the resistance value of the variable resistance element 19 is adjusted so that the potential at one end of the variable resistance element 19 becomes a reference voltage. Then, the adjusted resistance value of the variable resistance element 19 is kept, the switch element 17 is turned off, and the switch element 18 is turned on. Then, the resistance value of the variable resistance element 20 is adjusted so that the potential at one end of the variable resistance element 20 becomes a reference voltage. <P>COPYRIGHT: (C)2009,JPO&INPIT |
