Apparatus and methods for envelope tracking

A power amplifier system comprising:

• a power amplifier configured to amplify a radio frequency (RF) signal;
• an envelope tracker configured to generate a power amplifier supply voltage for the power amplifier using an envelope of the RF signal, the envelope tracker including a buck converter configured to generate a buck voltage from a battery voltage and a digital-to-analog converter (DAC) module configured to adjust a magnitude of the buck voltage based on the envelope of the RF signal to generate the power amplifier supply voltage, the DAC module including a push DAC and a pull DAC, the push DAC configured to increase the power amplifier supply voltage when the envelope of the RF signal increases and the pull DAC configured to decrease the power amplifier supply voltage when the envelope of the RF signal decreases, the buck converter including an NMOS transistor and a PMOS transistor each including a gate, a source and a drain, the gates of the NMOS and PMOS transistors electrically connected to the first and second buck control signals, respectively, the sources of the NMOS and PMOS transistors electrically connected to a power low supply voltage and the battery voltage, respectively, and the drains of the NMOS and PMOS transistors electrically connected together,
• a digital filter configured to receive the envelope of the RF signal and the power amplifier supply voltage and to generate a filtered envelope signal by filtering the envelope of the RF signal based at least in part on the power amplifier supply voltage;
• and
• a ripple control module configured to receive the filtered envelope signal and to generate a first buck control signal and a second buck control signal using the filtered envelope signal.

A method of envelope tracking in a power amplifier system, the method comprising:

• providing a power amplifier for amplifying a radio frequency (RF) signal;
• providing an envelope tracker for generating a supply voltage of the power amplifier using an envelope of the RF signal, the envelope tracker including a buck converter and a digital to analog (DAC) module, the DAC module including a push DAC and a pull DAC;
• generating a buck voltage from a battery voltage using the buck converter;
• adjusting the buck voltage using the DAC module to generate the supply voltage, a voltage magnitude of the adjustment based on the envelope of the RF signal;
• filtering the envelope of the RF signal using a digital filter;
• and
• delaying the filtered envelope signal before providing the filtered envelope signal to the DAC module.

A method of envelope tracking in a power amplifier system, the method comprising:

• providing a power amplifier for amplifying a radio frequency (RF) signal;
• providing an envelope tracker for generating a supply voltage of the power amplifier using an envelope of the RF signal, the envelope tracker including a buck converter and a digital to analog (DAC) module, the DAC module including a push DAC and a pull DAC;
• generating a buck voltage from a battery voltage using the buck converter;
• adjusting the buck voltage using the DAC module to generate the supply voltage, a voltage magnitude of the adjustment based on the envelope of the RF signal;
• filtering the envelope of the RF signal using a digital filter;
• shaping the filtered envelope signal to generate a shaped envelope signal;
• and
• converting the shaped envelope signal to a push DAC control signal and a pull DAC control signal, the push DAC and pull DAC control signals coded in a thermometer coding.