Patent ID: 8604882

Claim:
A circuit comprising: a source for providing a single ended signal; and a transformer for receiving the single ended signal; the transformer including first and second inductors; wherein the first and second inductors are mutually coupled; wherein when an operating frequency changes, a phase difference of currents flowing through the inductors changes, and therefore a phase difference between effective impedance of the first and second inductors changes to maintain a substantially 180 degree phase difference due to the mutual coupling, wherein the first inductor includes a first specified port coupled to one end of the first inductor and a third specified port at an opposite end of the first inductor; wherein the second inductor includes a second specified port coupled to one end of the second inductor and a fourth specified port at an opposite end of the second inductor; wherein the single-ended signal is inputted to the first specified port, wherein differential outputs are generated at the first specified port and the second specified port with a 180 degree phase shift, wherein third and fourth specified ports are connected to a first bias voltage.