| 摘要 |
PURPOSE:To increase the operation speed by supplying the gain control signal from outside to the transistor amplifier to give change to the gain and then selecting the desired transmission signal for transmission to the current addition type amplifier, thus realizing the miniaturization of the structure and the reduction of the crosstalk amount. CONSTITUTION:N units of transistor Tr amplifiers 3 function as the electronic switches of high output impedance connected to N units of input terminals 2. Thus the outputs of amplifiers 3 are connected in parallel to be supplied to current addition amplifier 5. Here control input terminal 4 is provided to amplifier 3, and the gain control signal is supplied to terminal 4 from outside. As a result, the gain of amplifier 3 is varied to turn on or off amplifier 3, and thus the desired transmission signal is selected to be sent to amplifier 5. In this way, the bipolar transmission signal can be selected directly without being converted into the unipolar signal by means of amplifiers 3 and 5, thus increasing the operation speed and realizing reduction of both the size of structure and the amount of crosstalk. |
