| 摘要 |
PURPOSE:Not only to decrease the number of elements but also to increase the input impedance, by forming a switch by use of a transistor TR and a diode D. CONSTITUTION:When a switch signal V5 given to the control terminal 18a is in a high level, both TR 11a and D 13a become OFF status, and an analog signal provided to the base of TR 11a does not appear in the output terminal 15. When the switch signal V5 is in a low level, TR 11a becomes ON status, and since the circuit formed by TR 11a and a resistor 12a is operated as an emitter-follower, the input impedance viewed from the input terminal 16a is increased. In this case, the diode 13a becomes ON status, and the output terminal 15 obtains the equal potential to the input terminal 16a. As for the system other than the foregoing, namely, TR 11b, a resistor 12b, D 13b..., the opration is performed in the same way. |
