| 摘要 |
PURPOSE:To realize recording with high fidelity by providing a dead band to AGC and limiting the increase/decrease of a gain depending on an input signal so as to compress the input signal to a degree not losing the dynamic range. CONSTITUTION:When an input signal Si is within a prescribed range, a diode D2 is turned off, a bias signal V1 is applied to a base of a transistor (Tr) Q1 through a resistor R2 and the gain of the system is made constant. On the other hand, when the signal Si is excessive and an output signal So exceeds a prescribed value, the diode D2 is conducted, a base voltage of the TrQ1 is increased and the gain is decreased to a degree where the signal So is not distorted. When the signal Si is decreased, the output level of a detection amplifier 3 is lower than a base-emitter voltage of the TrQ1, a diode D3 is conducted, a base potential of the TrQ1 is decreased and the gain is increased. In this case, the signal So is limited so as not to exceed a prescribed range of lower limit. |
