| 摘要 |
PURPOSE:To attain amplitude control without amplitude distortion even when a signal amplitude level is increased by providing a current control circuit supplying a control current in response to the signal amplitude to a base of each transistor (TR) pair so as to control each TR pair. CONSTITUTION:A current control circuit 36 is provided with a current mirror circuit 53 comprising TRs 42, 44, 46 and resistors 48, 50, 52 to extract a control current Ic flowing to a TR 38 in response to the TR pairs 20A, 20B. In this case, since the emitter area of the TR 44 is selected to be twice that of the TRs 42, 46, a control current 2Ic being twice the current Ic flows to the TR 44 and the current Ic flows to the TR 46. When the amplitude of an input signal Vi is large, the currents Ic, 2Ic are increased and when the amplitude is small, the currents are decreased, then the resistance of the TR pair 20A, 20B is con trolled in response to the amplitude level of an output signal V0. As a result, when the amplitude level of the signal V0 is large, the amplitude of the signal Vi is suppressed and when small, the suppressing state is relaxed, then the amplitude is controlled by the attenuation in response to the amplitude of the signal V0.
|
