Disclosed herein are signal amplifiers that provide impedance adjustments for different gain modes. The impedance adjustments are configured to result in a constant real impedance for an input signal at the amplifier. The amplifiers include a scalable impedance adjustment circuit that adjusts inductance and/or a device width to compensate for changes in the total impedance presented to an input signal. By providing impedance adjustments, the amplifiers reduce losses and improve performance by improving impedance matching over a range of gain modes.