| 摘要 |
PURPOSE: An active balun having symmetrical active load for small signals is provided which maintains impedances of two input ports of the active balun identical to each other to prevent generation of spurious signal, improving frequency response of the output terminal. CONSTITUTION: An active balun includes an amplification part(20) and an active load(30). The amplification part is constructed of the first FET(Q1) whose gate receives the first signal output from a mixer and whose source is connected to a constant current source(40), and the second FET(Q2) whose gate receives the second signal output from the mixer and whose source is connected to the source of the first FET and the constant current source. The active load includes the third FET(Q3) whose source is connected to the drain of the first FET, whose drain is connected to a power supply and whose gate and drain are connected to each other, and the fourth FET(Q4) whose source is connected to the drain of the second FET and outputs a signal, whose drain is connected to the power supply and whose gate is connected to the gate and drain of the third FET.
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