Patent ID: 7498861
Filing Date: 2009-03-03
Classification: H03D

Abstract:
1. A mixer, for converting input signals to voltage signals of other frequencies, comprising: a first impedance for receiving a positive output current and generating a first voltage signal at a first node, wherein the first node is coupled to a terminal of the first impedance; a second impedance for receiving a negative output current and generating a second voltage signal at a second node, wherein the second node is coupled to a terminal of the second impedance; a first NMOS transistor having a drain coupled to the first node and a gate for receiving a positive input signal; a second NMOS transistor having a drain coupled to the second node and a gate for receiving a negative input signal; a third NMOS transistor having a drain coupled to the drain of the first NMOS transistor and a gate for receiving the negative input signal; a fourth NMOS transistor having a drain coupled to the drain of the second NMOS transistor and a gate for receiving the positive input signal; a first switch having a first terminal coupled to a source of the first NMOS transistor and a second terminal coupled to a source of the second NMOS transistor, wherein the first switch is controlled by a positive local oscillation signal; a second switch having a first terminal coupled to a source of the third NMOS transistor and a second terminal coupled to a source of the fourth NMOS transistor, wherein the second switch is controlled by a negative local oscillation signal; a first current source, which is coupled to the source of the first NMOS transistor and provides a first bias current; a second current source, which is coupled to the source of the second NMOS transistor and provides a second bias current; a third current source, which is coupled to the source of the third NMOS transistor and provides a third bias current; and a fourth current source, which is coupled to the source of the fourth NMOS transistor and provides a fourth bias current.