The invention provides a signal amplifying stage, used in a signal receiver. The signal amplifying stage has: a fixed-gain low noise amplifier (LNA), amplifying an input signal; a variable-gain LNA (VG-LNA) array, amplifying the input signal, including a plurality of parallel VG-LNAs, the VG-LNA array being parallel with the fixed-gain LNA; a variable-gain amplifier (VGA), being in series with the fixed-gain LNA and the VG-LNA array, for amplifying output signals from the fixed-gain LNA and the VG-LNA array to generate an output signal; an attenuator, being in parallel with a combination of the fixed-gain LNA, the VG-LNA array and the VGA, for attenuating the input signal to generate the output signal; and a control loop, coupled to the VGA and the attenuator, for detecting power levels of the output signal to enable and control the fixed-gain LNA, the VG-LNA array, the VGA and the attenuator.