| 摘要 |
PURPOSE:To prevent the occurrence of noise such as switching sound accompanied with switching, by avoiding the change in DC voltage due to switching operation at the output stage. CONSTITUTION:When a selection signal is inputted to the terminal c, the a terminal side is ON and at low level with the terminal c at low level. On the other hand, the terminal a' side is OFF and it is biased to +V. Accordingly, the transistor Q3 is OFF, Q4 is ON, and the signal at the terminal a' is outputted to the terminal b. Next, when the terminal c is at high level, the terminal a side is OFF, and the terminal a' is ON. Accordingly, the terminal a is biased to +V and the terminal a' is at low level. Thus, the transistor Q3 is ON, Q4 is OFF, and the signal at the terminal a is outputted to the terminal b. By using the same characteristics of transistor for Q3 and Q4, only VBE and VBE' variation is present, and the DC voltage at the terminal b is not changed by switching operation. |
