Disclosed herein are signal amplifiers having a plurality of amplifier cores. Individual amplifier cores can be designed to enhance particular advantages while reducing other disadvantages. The signal amplifier can then switch between amplifier cores in a particular gain mode to achieve desired performance characteristics (e.g., improving noise figure or linearity). Examples of signal amplifiers disclosed herein include amplifier architectures with a low noise figure amplifier core that reduces the noise figure and a linearity boost amplifier core that increases linearity. The disclosed signal amplifiers can switch between a first active core and a second active core for a single or particular gain mode to achieve desired signal characteristics during different time periods.