| 摘要 |
PURPOSE:To arbitrarily set an impedance which has estimated a circuit side from a signal terminal, by connecting an emitter of an npn transistor to the signal terminal, and providing a variable current source between the signal terminal and a ground. CONSTITUTION:A collector, a base and an emitter of an npn transistor (hereinafter called TR) are connected to a power source terminal 1, a variable impedance circuit, and a signal terminal 3 connected to a high impedance circuit 4, respectively. Also, a collector, a base and an emitter of a TR 6 are connected to the terminal 3, bases of TRs 7, 8 and a collector of a TR 8, and a ground terminal 2, respectively. The collectors of the TRs 7, 8 are connected to a terminal 11 through resistances 9, 10, and the emitters are connected to the terminal 2. The TRs 7, 8 the resistances 9, 10 and the terminal 11 constitute a variable bias circuit. The TRs 7, 6 and 8 constitute first, second and third current mirror power sources, respectively. According to such a constitution, an impedance which has estimated a circuit side from the signal terminal can be set arbitrarily.
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