Single-ended to differential amplifier
View Patent ↗A circuit for single ended to differential conversion is disclosed. The circuit comprises a source for providing a single ended signal; and a transformer for receiving the single ended signal. The transformer includes first and second inductors. The first and second inductors are mutually coupled. When the 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.
1. 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.
2. The circuit of claim 1 wherein the transformer comprises a symmetric inductor.
3. The circuit of claim 1 wherein the transformer comprises an on chip transformer.
4. The circuit of claim 1 which includes a single ended amplifier coupled between the source and the transformer for providing an amplified single ended signal to the transformer.
5. A method comprising:
providing a single ended signal; and
receiving the single ended signal by a transformer, wherein the transformer includes first and second inductors such that 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, 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.
6. The method of claim 5 , wherein the transformer comprises a symmetric inductor.
7. The method of claim 5 . wherein the transformer comprises an on chip transformer.
8. The method of claim 5 , further comprising, amplifying the single ended signal before receiving the single ended signal by the transformer.