Variable-gain amplifier with degeneration circuit
This disclosure relates to variable-gain amplifiers that include degeneration circuits configured to adapt to a gain mode that is currently being implemented. For example, a variable-gain amplifier can operate in a plurality of gain modes to amplify a signal with different levels of amplification. The variable-gain amplifier can include a gain circuit configured to amplify a signal and a degeneration circuit coupled to the gain circuit. The degeneration circuit can include an inductor and a switching-capacitive arm coupled in parallel to the inductor. The degeneration circuit can operate based on a current gain mode to change an inductance for the variable-gain amplifier.
1. A variable-gain amplifier comprising:
a gain circuit configured to amplify a signal and to operate in a plurality of gain modes; and
a degeneration circuit coupled to the gain circuit, the degeneration circuit including an inductor and a switching-capacitive arm coupled in parallel to the inductor, the switching-capacitive arm including a capacitor and a switch coupled in series,
wherein the switch is configured to be placed in:
an open state when the gain circuit operates in a first gain mode from among the plurality of gain modes; and
a closed state when the gain circuit operates in a second gain mode from among the plurality of gain modes, the first gain mode being associated with more gain than the second gain mode.
2. The variable-gain amplifier of claim 1 wherein the switch includes at least one of a transistor or a mechanical switch.
3. The variable-gain amplifier of claim 1 wherein the switching-capacitive arm is a first switching-capacitive arm and the degeneration circuit further includes a second switching-capacitive arm coupled in parallel to the inductor.
4. The variable-gain amplifier of claim 1 wherein the gain circuit includes a transistor having a gate or base coupled to an input node and a drain or collector coupled to an output node, and the degeneration circuit is coupled to a source or emitter of the transistor.
5. The variable-gain amplifier of claim 1 wherein the variable-gain amplifier is implemented within a low noise amplifier.
6. The variable-gain amplifier of claim 1 wherein the gain circuit includes a transistor, and wherein the inductor, the switching-capacitive arm, and a source or emitter of the transistor are coupled to a common node.
7. A variable-gain amplifier comprising:
a transistor including a gate or base coupled to an input node and a drain or collector coupled to an output node; and
a degeneration circuit coupled to a source or emitter of the transistor, the degeneration circuit including an inductor and a switching-capacitive arm coupled in parallel to the inductor, the switching-capacitive arm including a capacitor and a switch coupled in series,
wherein the switch is configured to be placed in:
an open state when the variable-gain amplifier implements a first gain mode; and
a closed state when the variable-gain amplifier implements a second gain mode, the first gain mode being associated with more gain than the second gain mode.
8. The variable-gain amplifier of claim 7 wherein the switch includes one or more of a transistor or a mechanical switch.
9. The variable-gain amplifier of claim 7 wherein the switching-capacitive arm is a first switching-capacitive arm and the degeneration circuit further includes a second switching-capacitive arm coupled in parallel to the inductor.
10. The variable-gain amplifier of claim 7 wherein the variable-gain amplifier is implemented within a low noise amplifier.
11. The variable-gain amplifier of claim 7 wherein the inductor, the switching-capacitive arm, and the source or emitter of the transistor are coupled to a common node.
12. A radio-frequency module comprising:
a low noise amplifier configured to amplify a first signal;
a power amplifier configured to amplify a second signal; and
a controller coupled to at least one of the low noise amplifier or the power amplifier,
wherein at least one of the low noise amplifier or the power amplifier includes a transistor and a degeneration circuit coupled to the transistor, the transistor including a gate or base coupled to an input node and a drain or collector coupled to an output node, the degeneration circuit including an inductor and a switching-capacitive arm coupled in parallel to the inductor, the switching-capacitive arm including a capacitor and a switch coupled in series, and
wherein the controller is configured to:
control the switch to implement an open state for a first gain mode; and
control the switch to implement a closed state for a second gain mode, the first gain mode being associated with more gain than the second gain mode.
13. The radio-frequency module of claim 9 wherein the switch includes at least one of a transistor or a mechanical switch.
14. The radio-frequency module of claim 12 wherein the switching-capacitive arm is a first switching-capacitive arm and the degeneration circuit further includes a second switching-capacitive arm coupled in parallel to the inductor.
15. A radio-frequency device comprising:
the radio frequency module of claim 12 ; and
an antenna configured to receive the first signal and transmit the second signal.
16. The radio-frequency module of claim 12 wherein the inductor, the switching-capacitive arm, and a source or emitter of the transistor are coupled to a common node.