| 摘要 |
PROBLEM TO BE SOLVED: To provide a digital control variable resistance circuit, in which the number of resistances is reduced, the area of a board is made small, and arbitrary electric power capacity is obtained. SOLUTION: N(=n+1) pieces of resistances 11 which are connected to one another in series, N pieces of switches 12 which are connected to both ends of each resistance 11 in parallel, and a data resistor 15 of N-bit, which has bits corresponding to each switch 12 and opens the switch 12 when these bits are '1', are provided. A resistance value rk (k=0-n)Ωof each resistance 12 is, with rΩas resolution, set with 'rk =r*2<k> ', and a binary control data D to the data resistor 15 is, with XΩas a target resistance value, set with 'D=X/r'.
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