| 摘要 |
PURPOSE:To switch inputs and modes electronically, by using an electronic switch amplifier which has two pairs of noninversion and inversion input terminals and operates selectively either of input terminal pair. CONSTITUTION:Noise reduction circuits 11a and 11b have electronic switch amplifiers 12a and 12b and variable high-pass filters 13a and 13b, respectively, and variable high-pass filters 13a and 13b are different from each other in operation input level or operation frequency range. In respect to electronic switch amplifiers 12a and 12b, the common emitter of two differential amplifiers is grounded through differentially connected transistors, and either of differential amplifier is selected by a control signal applied to a terminal T. A control signal is applied from a terminal 15 to control selectively whether variable high-pass filters 13a and 13b should be inserted and connected to negative return circuits of electronic switch amplifiers 12a and 12b. |
