Abstract: Fast envelope tracking systems are provided herein. In certain embodiments, an envelope tracking system for a power amplifier includes a switching regulator and a differential error amplifier configured to operate in combination with one another to generate a power amplifier supply voltage for the power amplifier based on an envelope of a radio frequency (RF) signal amplified by the power amplifier. The envelope tracking system further includes a differential envelope amplifier configured to amplify a differential envelope signal to generate a single-ended envelope signal that changes in relation to the envelope of the RF signal. Additionally, the differential error amplifier generates an output current operable to adjust a voltage level of the power amplifier supply voltage based on comparing the single-ended envelope signal to a reference signal.

Abstract: Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker is provided for a power amplifier that amplifies an RF signal. The envelope tracker includes a multi-level switching circuit having an output that provides an output current that changes in relation to an envelope signal indicating an envelope of the RF signal when the envelope tracker is operating in an envelope tracking mode. The multi-level switching circuit includes a multi-level supply (MLS) modulator that receives multiple regulated voltages of different voltage levels, and an MLS control circuit that controls the selection of the MLS modulator over time based on the envelope signal. When transitioning the MLS modulator from selection of one regulated voltage level to another regulated voltage level, the MLS control circuit provides a soft transition to gradually switch the regulated voltage levels.

Abstract: Integrated Doherty power amplifiers are provided herein. In certain implementations, a Doherty power amplifier includes a carrier amplification stage that generates a carrier signal, a peaking amplification stage that generates a peaking signal, and an antenna structure that combines the carrier signal and the peaking signal. The antenna structure radiates a transmit wave in which the carrier signal and the peaking signal are combined with a phase shift.

Abstract: Envelope tracking systems with modeling for power amplifier supply voltage filtering are provided herein. In certain embodiments, an envelope tracking system includes a supply voltage filter, a power amplifier that receives a power amplifier supply voltage through the supply voltage filter, and an envelope tracker that generates the power amplifier supply voltage. The power amplifier provides amplification to a radio frequency (RF) signal that is generated based on digital signal data, and the envelope tracker generates the power amplifier supply voltage based on an envelope signal corresponding to an envelope of the RF signal. The envelope tracking system further includes digital modeling circuitry that models the supply voltage filter and operates to digitally compensate the digital signal data for effects of the supply voltage filter, such as distortion.

Abstract: Embodiments described herein relate to an envelope tracking system that uses a single-bit digital signal to encode an analog envelope tracking control signal, or envelope tracking signal for brevity. In certain embodiments, the envelope tracking system can estimate or measure the amplitude of the baseband signal. The envelope tracking system can further estimate the amplitude of the envelope of the RF signal. The system can convert the amplitude of the envelope signal to a single-bit digital signal, typically at a higher, oversample rate. The single-bit digital signal can be transmitted in, for example, a low-voltage differential signaling (LVDS) format, from a transceiver to an envelope tracker. An analog-to-digital converter (ADC or A/D) can convert the single-bit digital signal back to an analog envelope signal. Moreover, a driver can increase the power of the A/D output envelope signal to produce an envelope-tracking supply voltage for a power amplifier.

Abstract: Apparatus and methods for envelope tracking systems with automatic mode selection are provided herein. In certain configurations, a power amplifier system includes a power amplifier configured to provide amplification to a radio frequency signal and to receive power from a power amplifier supply voltage, and an envelope tracker including a signal bandwidth detection circuit configured to generate a detected bandwidth signal based on processing an envelope signal corresponding to an envelope of the radio frequency signal. The envelope tracker further includes a switch bank configured to receive a plurality of regulated voltages, a filter configured to filter an output of the switch bank to generate the power amplifier supply voltage, and a mode control circuit configured to control a filtering characteristic of the filter based on the detected bandwidth signal.

Abstract: Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker is provided for a power amplifier that amplifies an RF signal. The envelope tracker includes an error amplifier that controls a voltage level of a power amplifier supply voltage of the power amplifier based on amplifying a difference between a reference signal and an envelope signal indicating an envelope of the RF signal. The envelope tracker further includes a multi-level switching circuit that generates an error amplifier supply voltage based on sensing a current of the error amplifier, and uses the error amplifier supply voltage to power the error amplifier.

Abstract: High bandwidth envelope trackers are provided herein. In certain embodiments, an envelope tracking system for a power amplifier includes a switching regulator that operates in combination with a high bandwidth amplifier to generate a power amplifier supply voltage for the power amplifier based on an envelope of a radio frequency (RF) signal amplified by the power amplifier. The high bandwidth amplifier includes an output that generates an output current for adjusting the power amplifier supply voltage, a first input that receives a reference signal, and a second input that receives an envelope signal indicating the envelope of the RF signal. The second input has lower input impedance than the first input to provide a rapid transient response and high envelope tracking bandwidth.

Abstract: Fast envelope tracking systems are provided herein. In certain embodiments, an envelope tracking system for a power amplifier includes a switching regulator and a differential error amplifier configured to operate in combination with one another to generate a power amplifier supply voltage for the power amplifier based on an envelope of a radio frequency (RF) signal amplified by the power amplifier. The envelope tracking system further includes a differential envelope amplifier configured to amplify a differential envelope signal to generate a single-ended envelope signal that changes in relation to the envelope of the RF signal. Additionally, the differential error amplifier generates an output current operable to adjust a voltage level of the power amplifier supply voltage based on comparing the single-ended envelope signal to a reference signal.

Abstract: In some embodiments, an amplifier system can include an amplifier circuit having first and second amplifiers configured to amplify respective first and second portions of an input signal. Each of the first and second amplifiers can include a cascode stage with input and output transistors arranged in a cascode configuration. The amplifier system can further include an envelope tracking bias circuit coupled to the amplifier circuit and configured to provide a bias signal to the output transistor of the cascode stage of at least one of the first and second amplifiers. The amplifier system can further include a supply circuit configured to provide a non-envelope tracking supply voltage to the output transistor of the cascode stage of the at least one of the first and second amplifiers.

Abstract: Integrated Doherty power amplifiers are provided herein. In certain implementations, a Doherty power amplifier includes a carrier amplification stage that generates a carrier signal, a peaking amplification stage that generates a peaking signal, and an antenna structure that combines the carrier signal and the peaking signal. The antenna structure radiates a transmit wave in which the carrier signal and the peaking signal are combined with a phase shift.

Abstract: Apparatus and methods for power amplifier bias modulation for low bandwidth envelope tracking are provided herein. In certain embodiments, an envelope tracking system includes a power amplifier that amplifies an RF signal and a low bandwidth envelope tracker that generates a power amplifier supply voltage for the power amplifier based on an envelope of the RF signal. The envelope tracking system further includes a bias modulation circuit that modulates a bias signal of the power amplifier based on a voltage level of the power amplifier supply voltage.

Abstract: Multi-level envelope trackers with an analog interface are provided herein. In certain embodiments, an envelope tracking system for generating a power amplifier supply voltage for a power amplifier is provided. The envelope tracking system includes a multi-level supply (MLS) DC-to-DC converter that outputs multiple regulated voltages, an MLS modulator that controls selection of the regulated voltages over time based on an analog envelope signal corresponding to an envelope of the RF signal amplified by the power amplifier, and a modulator output filter coupled between an output of the MLS modulator and the power amplifier supply voltage.

Abstract: Multi-level envelope tracking systems with separate DC and AC paths are provided. In certain embodiments, an envelope tracking system for generating a power amplifier supply voltage for a power amplifier is provided. The envelope tracking system includes a multi-level supply (MLS) DC-to-DC converter that outputs multiple regulated voltages, an MLS modulator that controls selection of the regulated voltages over time based on an envelope signal corresponding to an envelope of a radio frequency (RF) signal amplified by the power amplifier, an AC path filter coupled between an output of the MLS modulator and the power amplifier supply voltage, and a DC path filter coupled between a DC voltage and the power amplifier supply voltage.

Abstract: Apparatus and methods for power amplifier bias modulation for multi-level supply envelope tracking are provided herein. In certain embodiments, an envelope tracking system includes a power amplifier that amplifies a radio frequency signal, a multi-level supply envelope tracker that generates a power amplifier supply voltage of the power amplifier based on an envelope signal indicating an envelope of the radio frequency signal, and a bias modulation circuit that modulates a bias of the power amplifier based on a voltage level of the power amplifier supply voltage.

Abstract: Multi-level envelope tracking systems with adjusted voltage steps are provided. In certain embodiments, an envelope tracking system for generating a power amplifier supply voltage for a power amplifier is provided. The envelope tracking system includes a multi-level supply (MLS) DC-to-DC converter that outputs multiple regulated voltages, an MLS modulator that controls selection of the regulated voltages over time based on an envelope signal corresponding to an envelope of a radio frequency (RF) signal amplified by the power amplifier, and a modulator output filter coupled between an output of the MLS modulator and the power amplifier supply voltage. The envelope tracking system further includes a switching point adaptation circuit configured to control the voltage level of the regulated voltages outputted by the MLS DC-to-DC converter based on a power level of the RF signal.

Abstract: Apparatus and methods for envelope tracking systems with automatic mode selection are provided herein. In certain configurations, a power amplifier system includes a power amplifier configured to provide amplification to a radio frequency signal and to receive power from a power amplifier supply voltage, and an envelope tracker including a signal bandwidth detection circuit configured to generate a detected bandwidth signal based on processing an envelope signal corresponding to an envelope of the radio frequency signal. The envelope tracker further includes a switch bank configured to receive a plurality of regulated voltages, a filter configured to filter an output of the switch bank to generate the power amplifier supply voltage, and a mode control circuit configured to control a filtering characteristic of the filter based on the detected bandwidth signal.

Abstract: Embodiments described herein relate to an envelope tracking system that uses a single-bit digital signal to encode an analog envelope tracking control signal, or envelope tracking signal for brevity. In certain embodiments, the envelope tracking system can estimate or measure the amplitude of the baseband signal. The envelope tracking system can further estimate the amplitude of the envelope of the RF signal. The system can convert the amplitude of the envelope signal to a single-bit digital signal, typically at a higher, oversample rate. The single-bit digital signal can be transmitted in, for example, a low-voltage differential signaling (LVDS) format, from a transceiver to an envelope tracker. An analog-to-digital converter (ADC or A/D) can convert the single-bit digital signal back to an analog envelope signal. Moreover, a driver can increase the power of the A/D output envelope signal to produce an envelope-tracking supply voltage for a power amplifier.

Abstract: Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker is provided for a power amplifier that amplifies an RF signal. The envelope tracker includes an error amplifier that controls a voltage level of a power amplifier supply voltage of the power amplifier based on amplifying a difference between a reference signal and an envelope signal indicating an envelope of the RF signal. The envelope tracker further includes a multi-level switching circuit that generates an error amplifier supply voltage based on sensing a current of the error amplifier, and uses the error amplifier supply voltage to power the error amplifier.

Abstract: High bandwidth envelope trackers are provided herein. In certain embodiments, an envelope tracking system for a power amplifier includes a switching regulator that operates in combination with a high bandwidth amplifier to generate a power amplifier supply voltage for the power amplifier based on an envelope of a radio frequency (RF) signal amplified by the power amplifier. The high bandwidth amplifier includes an output that generates an output current for adjusting the power amplifier supply voltage, a first input that receives a reference signal, and a second input that receives an envelope signal indicating the envelope of the RF signal. The second input has lower input impedance than the first input to provide a rapid transient response and high envelope tracking bandwidth.