| 摘要 |
An inventive FET balun transformer uses a positive power supply alone, not a negative one, thus downsizing a device including the balun transformer. In the FET balun transformer, a voltage supplied from the positive power supply is divided by a voltage divider consisting of a pair of resistors. The gate of a first FET is biased at a positive voltage, which is obtained by getting the divided supply voltage further divided by a first resistor. The gate of a second FET is grounded with an AC grounded capacitor interposed therebetween and biased at a positive voltage, which is obtained by getting the divided supply voltage further divided by a second resistor. Thus, the gate and source of a third FET do not have to be set at a negative potential, but may be grounded directly and via a biasing resistor, respectively. As a result, no negative power supply is needed for the third FET and the single-ended signal received at the input terminal can be converted into differential signals, which will be output through output terminals, while using the positive power supply alone.
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