Envelope tracking with dynamically configurable error amplifier
Apparatus and methods for power amplifier envelope tracking systems with automatic control of a slew rate and a mode of an error amplifier of the envelope tracking system. The envelope tracker can include a signal bandwidth detection circuit that processes the envelope signal to generate a detected bandwidth signal, and a control circuit that controls the slew rate of the error amplifier based on the detected signal bandwidth.
1 . An envelope tracker for a power amplifier, the envelope tracker comprising:
an input configured to receive an envelope signal corresponding to an envelope of a radio frequency signal;
an error amplifier configured to generate a power amplifier supply voltage, the error amplifier including a plurality of amplifying stages, one or more of the plurality of amplifying stages configured to be selectively activated to adjust a slew rate of the error amplifier;
a bandwidth detection circuit configured to generate a bandwidth signal indicating a bandwidth of the envelope signal; and
a control circuit configured to selectively activate the one or more of the plurality of amplifying stages of the error amplifier based on the bandwidth signal to adaptively adjust the slew rate to increase the slew rate of the error amplifier for larger envelope bandwidths and decrease the slew rate of the error amplifier for smaller envelope bandwidths by using one or more slew rate switches.
2 . The envelope tracker of claim 1 wherein the control circuit is configured to determine a number of resource blocks, the number of resource blocks corresponding to the bandwidth.
3 . The envelope tracker of claim 1 wherein the control circuit is configured to control a mode of the error amplifier based on the bandwidth.
4 . The envelope tracker of claim 1 wherein the envelope tracker further includes a DC-to-DC converter, and the error amplifier and the DC-to-DC converter operate in parallel with one another to generate the power amplifier supply voltage when the bandwidth satisfies a condition.
5 . A radio frequency front end module comprising:
a power amplifier configured to amplify a radio frequency signal and to receive power from a power amplifier supply voltage;
an envelope tracker configured to receive an envelope signal corresponding to an envelope of the radio frequency signal, the envelope tracker including a bandwidth detection circuit configured to generate a bandwidth signal indicating a bandwidth of the envelope signal, and an error amplifier configured to generate the power amplifier supply voltage, the error amplifier including a plurality of amplifying stages, one or more of the plurality of amplifying stages configured to be selectively activated to adjust a slew rate of the error amplifier, the envelope tracker further including a control circuit configured to selectively activate the one or more of the plurality of amplifying stages of the error amplifier based on the bandwidth signal to adaptively adjust the slew rate to increase the slew rate of the error amplifier for larger envelope bandwidths and decrease the slew rate of the error amplifier for smaller envelope bandwidths by using one or more slew rate switches.
6 . The front end module of claim 5 wherein the control circuit is configured to determine a number of resource blocks used by the radio frequency signal, the number of resource blocks corresponding to the bandwidth.
7 . The front end module of claim 5 wherein the control circuit is configured to control a mode of the error amplifier based on the bandwidth.
8 . The front end module of claim 5 wherein the envelope tracker further includes a DC-to-DC converter configured to operate in parallel with the error amplifier to generate the power amplifier supply voltage when the bandwidth satisfies a condition.
9 . A mobile device comprising:
a power amplifier system including a power amplifier configured to amplify a radio frequency signal and to receive power from a power amplifier supply voltage, the power amplifier system further including an envelope tracker including a bandwidth detection circuit configured to generate a bandwidth signal indicating a bandwidth of an envelope signal, and an error amplifier configured to generate the power amplifier supply voltage, the error amplifier including a plurality of amplifying stages, one or more of the plurality of amplifying stages configured to be selectively activated to adjust a slew rate of the error amplifier, the envelope tracker further including a control circuit configured to control the error amplifier to selectively activate the one or more of the plurality of amplifying stages based on the bandwidth signal to adaptively adjust the slew rate to increase the slew rate of the error amplifier for larger envelope bandwidths and decrease the slew rate of the error amplifier for smaller envelope bandwidths by using one or more slew rate switches; and
an antenna configured to transmit the amplified radio frequency signal.
10 . The mobile device of claim 9 wherein the control circuit is configured to determine a number of resource blocks, the number of resource blocks corresponding to the bandwidth.
11 . The mobile device of claim 9 wherein the control circuit is configured to control a mode of the error amplifier based on the bandwidth.
12 . The mobile device of claim 9 wherein the envelope tracker further includes a DC-to-DC converter, and the error amplifier and the DC-to-DC converter operate in parallel with one another to generate the power amplifier supply voltage when the bandwidth satisfies a condition.
13 . The envelope tracker of claim 4 further comprising an AC combiner configured to combine an output of the DC-to-DC converter and an output of the error amplifier, the AC combiner including a capacitor connected to an output of the error amplifier and a first inductor connected to an output of the DC-to-DC converter.
14 . The envelope tracker of claim 13 wherein the capacitor of the AC combiner is configured to filter out low frequency signal components and the first inductor of the AC combiner configured to filter out high frequency signal components.
15 . The envelope tracker of claim 14 further comprising a second inductor coupling the AC combiner to a supply terminal of the power amplifier.
16 . The front end module of claim 8 further comprising an AC combiner configured to combine an output of the DC-to-DC converter and an output of the error amplifier, the AC combiner including a capacitor connected to an output of the error amplifier and a first inductor connected to an output of the DC-to-DC converter.
17 . The front end module of claim 16 wherein the capacitor of the AC combiner is configured to filter out low frequency signal components and the first inductor of the AC combiner configured to filter out high frequency signal components.
18 . The front end module of claim 17 further comprising a second inductor coupling the AC combiner to a supply terminal of the power amplifier.
19 . The mobile device of claim 12 further comprising an AC combiner configured to combine an output of the DC-to-DC converter and an output of the error amplifier, the AC combiner including a capacitor connected to an output of the error amplifier and a first inductor connected to an output of the DC-to-DC converter.
20 . The mobile device of claim 19 wherein the capacitor of the AC combiner is configured to filter out low frequency signal components and the first inductor of the AC combiner configured to filter out high frequency signal components.