| 摘要 |
PURPOSE:To obtain a high speed highly accurate buffer amplifier provided with a low distortion factor by adding a current compensation circuit always compensating a current flowing to an active element to be constant in response to the change in a voltage given to a load of an emitter of the active element being a component of an emitter amplifier. CONSTITUTION:The current compensation circuit 5 is connected to the emitter of the active element 2. When a current flowing to the active element 2 is increased and its output voltage changes, a current flowing to a load 4 is changed. The output voltage change is given to a base of a transistor (TR) 6 via a level shift circuit 8 and a current flows to a dummy load 11. In selecting the impedance of the load 4 equal to the impedance of the dummy load 11, since the increment of the current flowing to the load 4 and the decrement of the collector current of a TR 7 are equal and the current through the active element 2 is unchanged. Thus, the current is always kept to a prescribed value independently of the excitation of the signal in the active element 2 and the mutual conductance (gm) and the current amplification factor beta are kept constant, then the distortion factor is improved.
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