An electronic device includes a processor, a modulator, and a power amplifier. The processor receives a baseband signal and executes a first ET shaping function on the baseband signal. The modulator receives the baseband signal, detects the magnitude of the baseband signal, and outputs the first voltage according to the magnitude of the baseband signal. The power amplifier outputs an amplified signal based on the first voltage. The first ET shaping function enables the relationship between the baseband signal and the first voltage to be Vpa=a|X|.sup.2+b. X is the baseband signal, Vpa is the first voltage, and a and b are constants. The look-up table records the relation curve between the power of the amplified signal and the first voltage when the second ET shaping function is used for envelope tracking.

One example discloses An equalizer, including: a first transistor and a second transistor both coupled to a first differential input (IP); a third transistor and a fourth transistor both coupled to a second differential input (IN); a first impedance (Z.sub.E1) coupled between the second transistor and the third transistor; a second impedance (Z.sub.E2) coupled between the first transistor and the fourth transistor; a first load resistance (R.sub.L1) coupled to a first supply node; a second load resistance (R.sub.L2) coupled to the first supply node; a current steering circuit coupled between the first, second, third and fourth transistors and the first and second load resistances; and a controller; wherein the controller is configured to adjust the current steering circuit to route a first percentage of an amplification current through the first impedance (Z.sub.E1) and a second percentage of the amplification current through the second impedance (Z.sub.E2).