| 摘要 |
A first current source injects an emitter bias current into a base-controlled amplifier transistor. A reference transistor identical to the amplifier transistor is connected to the battery to operate independently of the amplifier transistor. A second constant current source identical to the first injects the same emitter bias current into the reference transistor circuit. A circuit interconnects the bases of the reference and amplifier transistors so that the base current supplied to the amplifier transistor is identical to that drawn by the reference transistor to sustain the flow of emitter bias current. The amplifier transistor then offers a high input impedance to a signal source connected to its base.
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