| 摘要 |
PROBLEM TO BE SOLVED: To provide a D/A converter free from hung up sound, capable of increasing the number of steps for equivalently varying the resistance value of feedback resistance without causing increase of a circuit scale. SOLUTION: As for a variable resistor circuit 236, in a 1-bit D/A converter with a 0 data detecting soft mute function, resistors R21 to R34 are serially connected, first analog switches SW21 to SW34 to be selectively turned on/off in accordance with an output signal, except for the LSB of a counter are provided at respective connecting points to constitute a first digitally controlled variable resistor, resistors R35, R36 are connected in parallel, a second analog switch SW36 to be controlled by the LSB of the counter is serially connected to a resistor on one side to constitute a second digitally controlled variable resistor, both of the first and second digitally controlled variable resistors are serially connected and a third analog switch SW35 is connected to both of the ends to constitute a feedback resistor. Then, a feedback resistance value is reduced step by step to finally turn on the third analog switch to shortcircuit.
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