Apparatus and methods for envelope tracking systems

A method of generating a power amplifier supply voltage, the method comprising:

• generating a regulated voltage from a battery voltage using a DC-to-DC converter;
• controlling a magnitude of the regulated voltage based on a control voltage;
• generating an output current based on an envelope signal using an error amplifier;
• generating a power amplifier supply voltage for a power amplifier by adjusting the magnitude of the regulated voltage using the output current;
• controlling the DC-to-DC converter by changing a voltage level of the control voltage based at least in part on the power amplifier supply voltages;
• generating a high pass filtered power amplifier supply voltage based on filtering the power amplifier supply voltage using a high pass filter;
• generating a high frequency envelope signal by comparing the high pass filtered power amplifier supply voltage to the envelope signal using a first comparator;
• and
• providing the high frequency envelope signal to a non-inverting input of the error amplifier.

A radio frequency system comprising:

• a power management integrated circuit (PMIC) including a DC-to-DC converter configured to generate a regulated voltage from a battery voltage, the DC-to-DC converted configured to control a voltage level of the regulated voltage using a plurality of control voltages;
• a first power amplifier module including a first power amplifier configured to amplify a first radio frequency (RF) signal, a high pass filter configured to generate a high pass filtered power amplifier supply voltage based on high pass filtering of a first power amplifier supply voltage, a first comparator configured to generate a high frequency envelope signal based on comparing the high pass filtered power amplifier supply voltage to an envelope of the first RF signal, and a first error amplifier including a non-inverting input configured to receive the high frequency envelope signal and an output configured to generate the first power amplifier supply voltage for the first power amplifier by adjusting the voltage level of the regulated voltage based on the high frequency envelope signal, the first power amplifier module configured to change the voltage level of a first control voltage of the plurality of control voltages when the first power amplifier is enabled based at least in part on a voltage level of the first power amplifier supply voltage;
• and
• a second power amplifier module including a second power amplifier configured to amplify a second RF signal and a second error amplifier configured to generate a second power amplifier supply voltage for the second power amplifier by adjusting the voltage level of the regulated voltage based on an envelope of the second RF signal, the second power amplifier module configured to change the voltage level of a second control voltage of the plurality of control voltages when the second power amplifier is enabled based at least in part on a voltage level of the second power amplifier supply voltage.