| 摘要 |
PURPOSE:To improve greatly distortion factor characteristics without using a buffer amplifier for a D/A converter including a D/A converter, an analog switch and an LPF, by using an active filter to an LPF. CONSTITUTION:A digital signal given from a terminal 1 is converted into the analog voltage value corresponding to each value through a D/A converter 2 and fed to an analog switch SW3. The on-resistance value of the SW3 is set equal to the value including the fluctuated component caused by the input voltage and connected directly to an LPF8. The LPF8 is converted into an active filter having high input impedance characteristics. The signal passed through the LPF8 is amplified up to a prescribed level through an output amplifier 6 and then delivered through an output terminal 7. In such a way, distortion factor characteristics can be greatly improved without using a buffer amplifier of the SW3. |
