| 摘要 |
PURPOSE:To reduce the distortion and to increase the dynamic range by setting each control signal supplied from an automatic gain control circuit to a variable attenuator and a gain variable amplifier circuit so as to be opposite in the polarity. CONSTITUTION:An audio signal is attenuated to a permissible input level of a current control type amplifier circuit 22 by a current control type attenuator 21, amplified to a control level by the current control type amplifier circuit 22 and applied to an amplifier 23. Control circuits i1, i2 outputted from an automatic control circuit 24 detecting an output level of the amplifier 23 are opposite in the polarity with each other, and each amount of control current is outputted reciprocatingly by a differential circuit comprising transistors Q13, Q14. The automatic gain control characteristic is obtained while balancing the current control type attenuator 21 and the current control type amplifier circuit 22 in response to the increase/decrease in the input level. |
