| 摘要 |
PURPOSE: A variable resistor capable of changing resistance value in equal ratio, a variable gain amplifier using the same, and a variable cutoff frequency filter are provided to reduce the whole circuit area by removing a complex logic circuit. CONSTITUTION: A first resistance segment(210) and second resistance segments(211,212,213) are serially connected. The first switches(221,222,223) are connected to the second resistance segment in parallel. The second switches(231,232,233) are serially connected to the second resistance segment. The variable resistor(200) is controlled with the control signal of 2 bits. The first switch changes one connection state among second resistor segments according to control signals. The second switch is serially connected to the second resistance segment. |
