Configurable modal amplifier system
Configurable amplifier systems are described in which the power supply rail of a linear amplifier, e.g., a class A amplifier, is modulated by a switching amplifier, e.g., a class D amplifier, that may also be configured to operate independently of the linear amplifier. Techniques are also described by which the standing current of the output stage of a linear amplifier is modulated based on the input signal to the linear amplifier or based on modulation of the power supply rail of the linear amplifier.
1. An amplifier system, comprising:
a linear amplifier for amplifying an input signal, the linear amplifier having a power supply rail; and
a first switching amplifier, the first switching amplifier being configurable in a first mode to modulate the power supply rail of the linear amplifier based on the input signal to the linear amplifier, the first switching amplifier being configurable in a second mode to for signal amplification, wherein the first switching amplifier is configured to modulate the power supply rail of the linear amplifier only in its first mode.
2. The amplifier system of claim 1 , wherein the first switching amplifier is a class D amplifier.
3. The amplifier system of claim 1 , wherein the linear amplifier is a class A amplifier, a class B amplifier, or a class AB amplifier.
4. The amplifier system of claim 1 , wherein the first switching amplifier is configurable to operate in the first mode at a first average power efficiency and in the second mode at a second average power efficiency that is lower than the first average power efficiency.
5. The amplifier system of claim 1 , wherein the first switching amplifier is configurable to operate in the first mode at a first switching frequency and in the second mode at a second switching frequency that is higher than the first switching frequency.
6. The amplifier system of claim 1 , wherein the first switching amplifier is configurable to operate in the first mode at a first distortion level and in the second mode at a second distortion level that is lower than the first distortion level.
7. The amplifier system of claim 1 , wherein the first mode of the first switching amplifier is characterized by soft switching of an output stage of the first switching amplifier.
8. The amplifier system of claim 1 , wherein the first mode of the first switching amplifier is characterized by enforcement of a nonzero DC bias at an output of the first switching amplifier.
9. The amplifier system of claim 1 , further comprising first delay circuitry configured to delay the input signal before it is amplified by the linear amplifier.
10. The amplifier system of claim 9 , wherein the first delay circuitry is programmable to introduce a delay greater than or equal to zero, or wherein the first delay circuitry is configurable to be bypassed.
11. The amplifier system of claim 10 , further including second delay circuitry configured to delay the input signal before it is amplified by the first switching amplifier, wherein both the first delay circuitry and the second delay circuitry are independently programmable.
12. The amplifier system of claim 1 , further comprising a first chassis and a second chassis, the linear amplifier being integrated with the first chassis, and the first switching amplifier being integrated with the second chassis.
13. The amplifier system of claim 12 , wherein the amplifier system further comprises one or more sense terminals integrated with the first chassis and configured to provide feedback to the linear amplifier from a load driven by the linear amplifier.
14. The amplifier system of claim 12 , wherein a load driven by the linear amplifier is integrated with the first chassis.
15. The amplifier system of claim 1 , further comprising bias modulation circuitry configured to modulate a standing current of the linear amplifier based on the input signal to the linear amplifier or based on modulation of the power supply rail.
16. The amplifier system of claim 15 , wherein the bias modulation circuitry is configurable to modulate the standing current of the linear amplifier based on a specified load impedance.
17. The amplifier system of claim 1 , wherein the power supply rail is a positive power supply rail and the linear amplifier also has a negative power supply rail, the amplifier system further comprising a second switching amplifier, the second switching amplifier being configurable in a first mode to modulate the negative power supply rail of the linear amplifier based on the input signal to the linear amplifier, the second switching amplifier being configurable in a second mode for signal amplification, wherein the second switching amplifier is configured to modulate the negative power supply rail of the linear amplifier only in its first mode.
18. The amplifier system of claim 1 , wherein the first switching amplifier is configured to modulate the power supply rail of the linear amplifier in a substantially continuous manner.
19. The amplifier system of claim 1 , wherein the first switching amplifier is configured to drive the power supply rail of the linear amplifier to a plurality of discrete voltages.