| 摘要 |
PROBLEM TO BE SOLVED: To provide a tone control circuit with which a gain at a desired frequency can be continuously changed through a simple method. SOLUTION: A state parameter type active band-pass filter is constituted while using a transconductor amplifier composed of a differential amplifier 53 composed of transistors Q3 and Q4 and a pair of voltage/current converters 54 for converting the output voltage of an operational amplifier 51 composed of transistors Q1 and Q2 to input an input voltage ΔVin into a current. A conversion conductance gm of this transconductor amplifier is changed by the current of current source Ic according to a control signal from a control circuit 101. Corresponding to the change of this conversion conductance gm , a central frequency ω0 of this band-pass filter is changed. While using this band-pass filter, the tone control circuit is constituted. |
