| 摘要 |
PURPOSE:To decrease the number of the stages of electric adjustments in a process of manufacture by correcting the high frequency band of a reproduced signal through an equalizer amplifier behind the head amplifier of a magnetic head without providing the inductance of the magnetic head nor a resonance capacitor forming a resonance circuit to a head amplifier input stage. CONSTITUTION:When an amplifier having a flat output is constituted, the reproduction output of the head has such characteristics that the reproduction output decreases more and more as the frequency becomes higher and higher owing to various losses, so frequency characteristics after amplification are as shown by a dotted line 18. When demodulation is performed in said state, an upper and a lower side-band wave become unbalanced and inversion is caused. Consequently, the overall waveform has a peak at 4MHz, and an FM equalizer amplifier part 11 attains such peaking as to obtain a waveform 19 of left-right symmetry about said peak and performs phase compensation so that the phase is flat over the entire frequency range, thus constituting the head amplifier circuit which has excellent characteristics without a variable capacitor nor a variable resistor for Q adjustment which are necessary conventionally. |
