Coupled-inductance differential amplifier
View Patent ↗A differential amplifier that employs mutually coupled inductors to provide desired levels of inductance in a substantially smaller form factor in comparison to individual inductor components. Mutually coupled inductors according to the present teachings may also be used to increase common mode rejection in a differential amplifier.
1. A differential amplifier, comprising:
a pair of transistors;
a pair of inductors that provide impedance matching for the differential amplifier and that are arranged such that the inductors have a mutual inductance that increases when the differential amplifier is in a common mode.
2. The differential amplifier of claim 1 , wherein the inductors comprise a transformer.
3. The differential amplifier of claim 1 , wherein the inductors are arranged to provide input impedance matching for the differential amplifier.
4. The differential amplifier of claim 1 , wherein the inductors are coupled to a source terminal of each transistor.
5. The differential amplifier of claim 1 , wherein the inductors are arranged to provide noise control for the differential amplifier.
6. The differential amplifier of claim 1 , wherein the inductors are arranged to increase common mode rejection in the differential amplifier.
7. The differential amplifier of claim 1 , further comprising a second pair of inductors that are arranged to bias the transistors.
8. The differential amplifier of claim 7 , wherein the second pair of inductors are arranged to have a mutual inductance that increases when the differential amplifier is excited in the differential mode.
9. The differential amplifier of claim 8 , wherein the second pair of inductors comprise a transformer.
10. The differential amplifier of claim 9 , wherein the second pair of inductors are arranged to provide output impedance matching.
11. A method for providing a differential amplifier, comprising providing a pair of transistors; and arranging a pair of inductors for impedance matching to the differential amplifier such that the inductors have a mutual inductance that increases when the differential amplifier is in a common mode.
12. The method of claim 11 , wherein arranging comprises arranging the inductors for form a transformer.
13. The method of claim 11 , wherein arranging comprises arranging the inductors to provide input impedance matching for the differential amplifier.
14. The method of claim 11 , wherein arranging comprises coupling the inductors to a source terminal of each transistor.
15. The method of claim 11 , wherein arranging comprises coupling the inductors to provide noise control for the differential amplifier.
16. The method of claim 11 , wherein arranging comprises coupling the inductors to increase common mode rejection in the differential amplifier.
17. The method of claim 11 , further comprising arranging a second pair of inductors that bias the transistors.
18. The method of claim 17 , wherein arranging a second pair of inductors comprises arranging the second pair of inductors to have a mutual inductance that increases when the differential amplifier is excited in the differential mode.
19. The method of claim 18 , wherein arranging a second pair of inductors comprises arranging the second pair of inductors to form a transformer.
20. The method of claim 19 , wherein arranging a second pair of inductors comprises arranging the second pair of inductors to provide output impedance matching for the differential amplifier.