| 摘要 |
PURPOSE:To reduce noise generated due to a DC current with a simple constitution, by connecting a common emitter of a couple of transistors (TR) to a constant current source so as to flow a constant current to the common emitter and reducing the DC current flowing to the couple of TRs by the amount in response to the constant current. CONSTITUTION:When a sinusoidal input signal voltage of a maximum amplitude is impressed to an input terminal IN, since a current IO flows to the common emitter of the TRs Q1, Q2 from the constant current source IO, a collector current as shown in figure flows to the TRQ2. Although a DC current more than the required minimum current flows to an amplifier of conventional systems superimposingly, the amplifier of this invention calls for the required minimum DC current. Then, noise due to current is lower in the amplifier of this invention in comparison with the conventional system. Further, the amplitude of the constant current from the constant current source IO should be set to a value so that a current in response to the input signal voltage of the maximum amplitude can be given to the TRQ2. |
