The ultimate goal of the modern wireless communication industry is the full integration of digital, analog, and radio frequency (RF) functions. The most successful solution for such demands has been complementary metal oxide semiconductor (CMOS) technology, thanks to its cost-effective material and great versatility. Power amplifier (PA), the biggest bottleneck to integrate in a single-chip transceiver in wireless communications, significantly influences overall system performance. Recent advanced wireless communication systems demand a power amplifier that can simultaneously support different communication standards. A fully integrated single-chip tunable CMOS power amplifier is the best solution in terms of the cost and level of integration with other functional blocks of an RF transceiver. This work, for the first time, proposes a fully integrated band-switchable RF power amplifier by using a novel approach towards switching the matching networks. In this approach, which is called Bit Optimized Reconfigurable Network (BORN), two matching networks which can be controlled by digital bits will provide three operating frequency bands for the power amplifier. In order to implementing the proposed BORN PA, a robust high-power RF switch is presented by using resistive body floating technique and 6-terminal triple-well NMOS. The proposed BORN PA delivers measured saturated output power (Psat) of 21.25/22.25/ 23.0dBm at 960MHz/1317MHz/1750MHz, respectively. Moreover, the proposed BORN PA provides respective 3-dB bandwidth of 400MHz/425MHz/550MHz, output 1-dB compression point (P1dB) of 19.5dBm/20.0dBm/21.0dBm, and power-added efficiency (PAE) of 9/11/13% at three targeted frequency bands, respectively. The promising results show that the proposed BORN PA can be a practical solution for RF multiband applications in terms of the cost and level of integration with other functional blocks of an RF transceiver.