| 摘要 |
PURPOSE:To attain the simplicity of constitution by providing a couple of amplifiers given with a prescribed DC bias from a common bias power supply so as to attain the adjustment of an output signal level of one amplifier based on an external control input. CONSTITUTION:A prescribed DC bias is given to the amplifiers 2, 4 and a magnetic head 8 from the common DC bias power supply 10, a reproducing signal of the magnetic head 8 is amplified by the amplifier 2 and its amplified output is extracted from an output terminal 34. On the other hand, the reproducing signal from the magnetic head 8 is inputted to the amplifier 4, each operating current of differential amplifiers 40, 42 is controlled by a muting circuit 44 and its output signal level is adjusted based on a muting control voltage Vc given to a control input terminal 72. Thus, an output attended with a signal level and other output not attended with the signal level are outputted separately in this way, the frequency characteristic and the amplification gain of each output are set optionally and also the simplicity of constitution is attained. |
