A peak detector using a charge pump is provided. The peak detector includes a differential amplifier configured to receive an input signal to be detected through an input node and amplify the received signal; a current control logic configured to create two or more current control signals by comparing a signal output from the differential amplifier with two or more reference voltages; a mirror current source portion comprising two or more mirror current sources configured to be driven respectively by the current control signals from the current control logic; a capacitor configured to be charged or discharged by currents output from the mirror current sources; and a reset circuit configured to reset a voltage of the capacitor.