| 摘要 |
PURPOSE:To obtain a stable frequency characteristic by feeding the output of a feedback amplifier back to the input of a main amplifier, grounding the input of the main amplifier by a capacitor to suppress resonance peak with an induced magnetic head at the input. CONSTITUTION:The signal of a magnetic head 1 is amplified by a main amplifier 3 and outputted and through a feedback amplifier 4 which amplifies a low frequency component with a high gain and a high frequency component with a low gain, a frequency characteristic (a) shown in a figure is obtained. For the output, the feedback amount of the high frequency component to the input of the main amplifier 3 is controlled by a low-pass filter, which is composed of a resistor 6 and a capacitor 9 grounding the base of an input transistor in the main amplifier 3, and closed to a track in the figure and the resonance peak with the induced magnetic head at the input is suppressed. Thus, the stable frequency characteristic can be obtained. |
