| 摘要 |
PURPOSE:To improve the DC stability of a D/A conversion part, by feeding back a DC component contained in the output of the D/A conversion part to an operational amplifier at the post stage of the D/A conversion part. CONSTITUTION:When an input signal A is supplied, a D/A converter 1 outputs a current signal with an analog value corresponding to the input signal with a digital value and this current signal is amplified by the operational amplifier 2, and supplied to an analog switch 3 as a voltage value signal. The analog switch 3 is controlled by switching based upon a sampling pulse B supplied synchronously with the input signal A. The output of the analog switch 3 is supplied as an audio signal to an output terminal 12 through a low-pass filter 4 and an amplifier 11. The DC component in the analog audio signal is detected by the offset control circuit 16 consisting of a low-pass filter 14 and an amplifier 15 and then fed back to the offset control terminal of the operational amplifier 2. |
