Amplifier circuit using voltage-to-current conversion to achieve unity feedback factor and input common-mode rejection for linear amplifier and associated envelope tracking supply modulator using the same

An envelope tracking supply modulator comprising:

• an amplifier circuit, arranged to receive an envelope input, and generate an amplifier output according to the envelope input, wherein the amplifier output is involved in setting a modulated supply voltage of a power amplifier, and the amplifier circuit comprises:
• a voltage-to-current conversion circuit, arranged to generate a current signal according to the envelope input, wherein the voltage-to-current conversion circuit comprises:
• an operational transconductance amplifier (OTA), arranged to output the current signal at an output port of the OTA;
• and
• a current-to-voltage conversion circuit, arranged to generate the amplifier output according to the current signal, wherein the current-to-voltage conversion circuit comprises:
• a linear amplifier (LA), wherein an input port of the LA is coupled to the output port of the OTA, an output port of the LA is coupled to the PA, and the amplifier output is derived from an output signal at the output port of the LA.