Amplification system with differential envelope-based bias
Disclosed herein are amplification systems that are dynamically biased based on a signal indicative of differential envelope of an input radio-frequency (RF) signal being amplified. The amplification systems include a cascode amplifier configured to amplify the RF signal to generate an output RF signal when one of the transistors of the cascode amplifier is biased by a combination of the input RF signal and a biasing signal while the other transistor of the cascode amplifier is biased by a processed differential envelope signal. The cascode amplifier also receives a combination of a processed differential envelope signal and a supply voltage to generate the output RF signal. The biasing signal can improve or enhance the linearity of amplification systems.
1. An amplification system comprising:
a first differential amplifier configured to receive a differential envelope signal and to provide a first processed envelope signal;
a second differential amplifier configured to receive the differential envelope signal and to provide a second processed envelope signal;
an envelope tracker configured to receive the first processed envelope signal and to provide an envelope tracking signal; and
a cascode amplifier having a first transistor and a second transistor configured to generate an output RF signal that is an amplified version of an input RF signal, the first transistor biased by a combination of a biasing signal and the input RF signal, the second transistor biased by the second processed envelope signal, the second transistor configured to receive an envelope-based supply voltage that is a combination of the envelope tracking signal and a supply voltage.
2. The amplification system of claim 1 wherein a drain of the first transistor is coupled to an output port to provide the output RF signal.
3. The amplification system of claim 2 wherein the drain of the first transistor is further coupled to an envelope-based supply node that combines the envelope tracker and the supply voltage.
4. The amplification system of claim 3 wherein the envelope-based supply node is further coupled to a reference potential node through a capacitor.
5. The amplification system of claim 4 wherein the envelope-supply node is coupled to the drain of the first transistor through an inductor.
6. The amplification system of claim 1 further comprising an RC combiner configured to combine the input RF signal and the biasing signal to bias the first transistor.
7. The amplification system of claim 1 further comprising an LC combiner configured to combine the envelope tracking signal and the supply voltage to generate the envelope-based supply voltage.
8. The amplification system of claim 1 wherein a drain of the second transistor and a source of the first transistor are coupled together and to an intermediate cascode node that is coupled to a reference potential node through a capacitor.
9. The amplification system of claim 1 further comprising a delay component coupled to the second differential amplifier and to the first transistor.
10. The amplification system of claim 1 further comprising a non-linear device coupled to the second differential amplifier and to the first transistor.
11. The amplification system of claim 1 further comprising a buffer coupled to the second differential amplifier and to the first transistor.
12. The amplification system of claim 1 further comprising a non-linear device, a delay component, and a buffer coupled in series between the second differential amplifier and the first transistor.
13. The amplification system of claim 1 wherein the envelope tracking signal is indicative of an envelope of the input RF signal.
14. The amplification system of claim 1 further comprising an output matching component coupled to the first transistor and an input matching component coupled to the second transistor.
15. A radio-frequency (RF) module comprising:
a packaging substrate configured to receive a plurality of components; and
an amplification system implemented on the packaging substrate, the amplification system including a first differential amplifier configured to receive a differential envelope signal and to provide a first processed envelope signal; a second differential amplifier configured to receive the differential envelope signal and to provide a second processed envelope signal; an envelope tracker configured to receive the first processed envelope signal and to provide an envelope tracking signal; and a cascode amplifier having a first transistor and a second transistor configured to generate an output RF signal that is an amplified version of an input RF signal, the first transistor biased by a combination of a biasing signal and the input RF signal, the second transistor biased by the second processed envelope signal, the second transistor configured to receive an envelope-based supply voltage that is a combination of the envelope tracking signal and a supply voltage.
16. The RF module of claim 15 wherein the amplification system further includes an output matching component coupled to the first transistor and an input matching component coupled to the second transistor.
17. The RF module of claim 15 wherein the amplification system further includes a non-linear device, a delay component, and a buffer coupled in series between the second differential amplifier and the first transistor.
18. The RF module of claim 15 wherein the envelope tracking signal is indicative of an envelope of the input RF signal.
19. A wireless device comprising:
a transceiver configured to generate a radio-frequency (RF) signal;
a front-end module (FEM) in communication with the transceiver, the FEM including a packaging substrate configured to receive a plurality of components, the FEM further including an amplification system implemented on the packaging substrate, the amplification system including a first differential amplifier configured to receive a differential envelope signal and to provide a first processed envelope signal; a second differential amplifier configured to receive the differential envelope signal and to provide a second processed envelope signal; an envelope tracker configured to receive the first processed envelope signal and to provide an envelope tracking signal; and a cascode amplifier having a first transistor and a second transistor configured to generate an output RF signal that is an amplified version of an input RF signal, the first transistor biased by a combination of a biasing signal and the input RF signal, the second transistor biased by the second processed envelope signal, the second transistor configured to receive an envelope-based supply voltage that is a combination of the envelope tracking signal and a supply voltage; and
an antenna in communication with the FEM, the antenna configured to transmit the output RF signal received from the amplification system.
20. The wireless device of claim 19 wherein the envelope tracking signal is indicative of an envelope of the input RF signal.