| 摘要 |
A mixer includes a doubly-balanced mixer core, an RF input section coupled to the mixer core, and a biasing circuit coupled to the RF input section. The RF input section includes a first transistor coupled to a first input of the mixer core for supplying a first current thereto. The base of the first transistor is driven by an RF input current, as a result, the first current is responsive to the RF input current. The RF input section also includes a current mirror coupled to the first transistor, which mirrors the sum of the first current and the RF input current to produce a second current that is complementary to the first current for small variations of the RF input current. The current mirror is coupled to a second input of the mixer core to supply the second current thereto. A biasing circuit is coupled to the RF input section to establish a quiescent value of the first current. Padding resistor can also be used in the RF input section to provide a predetermined input impedance to the RF input current.
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