A re-configurable low noise amplifier utilizing feedback capacitors is disclosed. The low noise amplifier has output transistors, capacitor switch cells, and capacitance distributors all in an output portion. The output transistors are for controlling selection of a specific frequency band in a wide band of frequencies. The capacitor switch cells are for adjusting a harmonic frequency for the specific frequency band. The capacitance distributor is for determining an amount of gain, and according to the gain, an output impedance feeds back to an input portion of the low noise amplifier for input matching. Since the output portion is at high impedance and suitable for a wide band of frequencies, input matching not only makes the low noise amplifier applicable to kinds of wireless communication standards, but also fulfills high gain and low noise figure.