| 摘要 |
PROBLEM TO BE SOLVED: To reduce an effect of a path to a buzzer output, to miniaturize a circuit, to improve the stability of the buzzer output and to make circuit constitution independent of the number of bits of the control data. SOLUTION: A path for controlling the gate voltage of an FET is composed of one system by adopting negative feedback circuit configuration where the output of a buzzer 11 is controlled by controlling a drain current of an FET4 whose gate voltage is controlled by an operational amplifier 3 receiving the source output of the FET 4 as an inverted input, and the stability of the buzzer output is improved. The circuit constitution independent of the number of bits of the control data is obtained by giving a variable source 2 whose output is changed according to the control data of a logic part 1 to the operational amplifier 3 as a non-inverted input.
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