| 摘要 |
PROBLEM TO BE SOLVED: To provide an analog reference voltage generating circuit used for an audio amplifier or a headphone amplifier that suppresses a pop noise (click noise) generated when an analog reference voltage rises toward a prescribed voltage after release of a standby state. SOLUTION: The analog reference voltage generating circuit 15 is configured with: a reference voltage (VREF) generating circuit 5; a ramp waveform generating circuit 10 comprising a constant current source 13, a capacitor C7, and a comparator 16 for controlling a switch SW1; filter circuits LPF 1, LPF 2 comprising resistors R1, R2 and capacitors C7, C5 and for smoothing a leading waveform; and a saturation time reduction circuit 11 comprising a MOS transistor MOS TR and a gate voltage controlling arithmetic circuit 17. Thus, after release of the standby state, the analog reference voltage generating circuit 15 suppresses production of a pop noise (click noise) while generating an analog reference voltage AGND in a comparatively short time. COPYRIGHT: (C)2006,JPO&NCIPI
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