Systems and methods for mitigating distortion in single-ended amplifiers
View Patent ↗Systems and methods which implement degeneration circuitry in a single-ended amplifier circuit to mitigate distortion associated with one or more amplifier components are disclosed. A degeneration circuit of embodiments adds an impedance to cancel the second-order distortion of an amplifier transistor of a single-ended amplifier circuit. A bias circuit may be provided to minimize bias offset between an amplifier transistor and a corresponding degeneration transistor.
1. A system comprising:
an active amplifier component configured to provide amplification with respect to an attribute of a signal; and
a degeneration circuit coupled to the amplifier component and having a degeneration component with characteristics matching characteristics of the amplifier component and operable to provide cancellation of distortion associated with the amplifier component, wherein the degeneration component is disposed in a circuit configuration to experience increased current flow in proportion to a decrease in current flow experienced by the amplifier component and to experience decreased current flow in proportion to an increase in current flow experienced by the amplifier component.
2. The system of claim 1 , wherein the degeneration circuit comprises:
a bias circuit coupling a node of the amplifier component to a corresponding node of the degeneration component and providing a bias voltage to the node of the degeneration component equal to a bias voltage of the node of the amplifier component.
3. The system of claim 2 , wherein the bias circuit comprises:
a unity gain amplifier.
4. The system of claim 2 , wherein the bias circuit comprises:
an operational amplifier.
5. The system of claim 2 , wherein the bias circuit comprises:
a radio frequency (RF) filter; and
a direct current (DC) amplifier.
6. The system of claim 2 , wherein the amplifier component comprises a transistor and the degeneration component comprises a transistor matching the amplifier component transistor.
7. The system of claim 6 , wherein the node of the amplifier component comprises a base of the amplifier component transistor and the corresponding node of the degeneration component comprise a base of the degeneration component transistor.
8. The system of claim 2 , wherein the degeneration circuit further comprises:
at least one component disposed to provide the degeneration component in a low impedance circuit configuration with respect to the bias voltage.
9. The system of claim 8 , wherein the at least one component comprises:
a capacitor.
10. A single-ended input, single-ended output amplifier circuit comprising:
an amplifier transistor;
a degeneration transistor coupled to the amplifier transistor, the degeneration transistor having characteristics matching characteristics of the amplifier transistor and disposed in a circuit configuration to provide cancellation of distortion associated with the amplifier transistor; and
a bias circuit coupling a node of the amplifier transistor to a corresponding node of the degeneration transistor and providing a bias voltage to the node of the degeneration transistor equal to a bias voltage of the node of the amplifier transistor.
11. The amplifier circuit of claim 10 , wherein the circuit configuration of the degeneration transistor provides increased current flow in the degeneration transistor in proportion to a decrease in current flow in the amplifier transistor and decreased current flow in the degeneration transistor in proportion to an increase in current flow in the amplifier transistor.
12. The amplifier circuit of claim 10 , wherein the bias circuit comprises:
a unity gain amplifier.
13. The amplifier circuit of claim 10 , wherein the bias circuit comprises:
an operational amplifier in a negative feedback configuration.
14. The amplifier circuit of claim 10 , wherein the bias circuit comprises:
a radio frequency (RF) filter; and
a direct current (DC) amplifier.
15. The amplifier circuit of claim 10 , wherein the node of the amplifier transistor and the corresponding node of the degeneration transistor each comprises a transistor base.
16. The amplifier circuit of claim 10 , further comprising:
at least one component disposed to provide the degeneration transistor in a low impedance circuit configuration with respect to the bias voltage.
17. The amplifier circuit of claim 16 , wherein the at least one component comprises:
a capacitor.
18. A method comprising:
providing a single-ended input, single-ended output amplifier circuit having an amplifier transistor and a degeneration transistor; and
operating the amplifier circuit to provide increased current flow in the degeneration transistor in proportion to a decrease in current flow in the amplifier transistor and decreased current flow in the degeneration transistor in proportion to an increase in current flow in the amplifier transistor to thereby provide cancellation of distortion associated with the amplifier transistor.
19. The method of claim 18 , wherein the operating the amplifier circuit comprises:
biasing the degeneration transistor with a bias voltage of the amplifier transistor.
20. The method of claim 19 , wherein the biasing the degeneration transistor comprises:
coupling a node of the amplifier transistor to a corresponding node of the degeneration transistor using a biasing circuit.
21. The method of claim 20 , wherein the biasing circuit comprises a unity gain amplifier.
22. The method of claim 21 , wherein the biasing circuit comprises a radio frequency (RF) filter.
23. The method of claim 20 , wherein the node of the amplifier transistor and the corresponding node of the degeneration transistor each comprise a transistor base node.
24. The method of claim 20 , further comprising:
providing the corresponding node of the degeneration transistor in a low impedance configuration.