This invention is intended to propose new topology power amplifier module for high resolution vehicular radar. This invention described an excellent gain flatness CMOS power amplifier (PA) for ultra-wideband (UWB) applications at operating frequency 3.0-7.0 GHz using CMOS technology. The PA consists of two stages of amplifiers. The first stage consists of current-reused cascoded common-source (CS) structure, where the first two transistors is a CS amplifier. The impedance of inductor in the first stage is adequately large to provide a high impedance path to block the signal at the desired bandwidth. The current-reused helps to amplify the input signal twice, thus high gain PA is obtained. A narrow band characteristic composed by the resonance circuit in the first stage is employed to enhance the gain at the upper end of the desired band. In addition, inductor at the first stage which is connected between transistor and supply voltage is inductive peaking to obtain the high gain at the lower frequency. The inter-stage inductor and a resistive feedback at the second stage are employed to obtain the gain flatness, while shunt-shunt feedback helps to enhance the bandwidth and improve the output wideband matching. The first stage and second stage are connected with a series peaking inductor for extending the high frequency response and improve gain flatness. The second stage is CS amplifier with resistive feedback helps to achieve excellent gain flatness and inductor is used as a load for CS amplifier.