A portable communication device comprising: a first communication chip including a first amplifier configured to amplify a first transmission signal for transmission to an external device, a first comparator, and a first linear regulator configured to provide a first voltage to the first amplifier based on an envelope corresponding to a first designated frequency band of the first transmission signal; a second communication chip including a second amplifier configured to amplify a second transmission signal for transmission to an external device; an ET modulator disposed outside of the first communication chip and the second communication chip, including a switching regulator, a second comparator, a second linear regulator configured to provide a second voltage to the second amplifier based on an envelope corresponding to a second designated frequency band of the second transmission signal, and a multiplexer configured to control a voltage input to the switching regulator; a control circuitry, wherein the control circuitry is configured to supply a third voltage to the first amplifier using the switching regulator based on an envelope corresponding to a third designated frequency band of the first transmission signal when the first transmission signal is being amplified, wherein the control circuitry is configured to supply a fourth voltage to the second amplifier using the switching regulator based on an envelope corresponding to the third designated frequency band of the second transmission signal when the second transmission signal is being amplified, wherein the first comparator is configured to compare the first voltage and the third voltage, and the control circuitry is configured to control the multiplexer to output a signal from the first comparator as an input signal to the switching regulator when the first transmission signal is being amplified, and wherein the second comparator is configured to compare the second voltage and the fourth voltage and the control circuitry is configured to control the multiplexer to output a signal from the second comparator as an input signal to the switching regulator when the second transmission signal is being amplified. a first communication chip including a first amplifier configured to amplify a first transmission signal for transmission to an external device, a first comparator, and a first linear regulator configured to provide a first voltage to the first amplifier based on an envelope corresponding to a first designated frequency band of the first transmission signal; a second communication chip including a second amplifier configured to amplify a second transmission signal for transmission to an external device; an ET modulator disposed outside of the first communication chip and the second communication chip, including a switching regulator, a second comparator, a second linear regulator configured to provide a second voltage to the second amplifier based on an envelope corresponding to a second designated frequency band of the second transmission signal, and a multiplexer configured to control a voltage input to the switching regulator; a control circuitry, wherein the control circuitry is configured to supply a third voltage to the first amplifier using the switching regulator based on an envelope corresponding to a third designated frequency band of the first transmission signal when the first transmission signal is being amplified, wherein the control circuitry is configured to supply a fourth voltage to the second amplifier using the switching regulator based on an envelope corresponding to the third designated frequency band of the second transmission signal when the second transmission signal is being amplified, wherein the first comparator is configured to compare the first voltage and the third voltage, and the control circuitry is configured to control the multiplexer to output a signal from the first comparator as an input signal to the switching regulator when the first transmission signal is being amplified, and wherein the second comparator is configured to compare the second voltage and the fourth voltage and the control circuitry is configured to control the multiplexer to output a signal from the second comparator as an input signal to the switching regulator when the second transmission signal is being amplified.