Abstract: An active bandpass filter is disclosed herein. The active bandpass filter has N transmission lines, N negative resistant circuits, a DC circuit, and at least (N?1) coupling circuit. Each transmission line has a first end and a second end. Each negative resistant circuit has a third end and a fourth end and is electrically coupled with a related transmission line, wherein the third end and the fourth end are electrically coupled with the first end and second end, respectively. The DC circuit provides a bias voltage for N negative resistant circuits, wherein the DC circuit electrically couples with N transmission lines via N coupling elements. Each coupling circuit has a fifth end and a sixth end and is electrically coupled with any two transmission lines, wherein the fifth end and sixth end are electrically coupled with the second end and the first end, respectively.

Abstract: A circuit for generating a reference voltage at an output node comprises a first branch, a second branch, and a main current source. The first branch is electrically connected between a first terminal and a second terminal of the circuit, and comprises at least one first semiconductor device. Each first semiconductor device comprises a first node and a second node. The second branch is electrically connected between the first terminal and the second terminal of the circuit, and comprises at least one second semiconductor device and a branch current source. Each second semiconductor device comprises a first node and a second node. The branch current source is serially connected to the second transistor. The main current source is electrically connected to one of the first terminal and the second terminal of the circuit. The output node is in the first branch or the second branch.

Abstract: An active bandpass filter is disclosed herein. The active bandpass filter has N transmission lines, N negative resistant circuits, a DC circuit, and at least (N?1) coupling circuit. Each transmission line has a first end and a second end. Each negative resistant circuit has a third end and a fourth end and is electrically coupled with a related transmission line, wherein the third end and the fourth end are electrically coupled with the first end and second end, respectively. The DC circuit provides a bias voltage for N negative resistant circuits, wherein the DC circuit electrically couples with N transmission lines via N coupling elements. Each coupling circuit has a fifth end and a sixth end and is electrically coupled with any two transmission lines, wherein the fifth end and sixth end are electrically coupled with the second end and the first end, respectively.