| 摘要 |
PURPOSE:To obtain a voice output with less feeling of disorder by decreasing the internal input impedance at the start of operation of an amplifier and then increasing it gradually so as to increase gradually the output after the 1st point of time is elapsed in the titled muting circuit inhibiting the operation of an amplifier circuit up to the 1st point of time after application of power. CONSTITUTION:When a cpacitor C5 is charged by application of power and a level of a point F reaches a prescribed value, a transistor (TR) 10 is turned on and a load TR12 of a differential input amplifier circuit is turned on and the amplification operation is started. An AGC circuit is activated by a current of a TR19 and an input signal is attenuated. When a potential at the point F is increased, the TR19 is turned off and the current of the TR19 is changed during this time, resulting that the current of a TR20 is changed. Thus, the internal input impedance (impedance viewed from a point A) is changed and the input voltage to the amplifier circuit is changed. |
