Amplifiers with boosted or deboosted source degeneration inductance are disclosed. In an exemplary design, an apparatus includes an amplifier circuit and a feedback circuit. The amplifier circuit receives an input signal and provides an output signal and includes a source degeneration inductor. The feedback circuit is coupled between a node of the amplifier circuit and the source degeneration inductor. The feedback circuit provides feedback to vary an input impedance of an amplifier including the amplifier circuit and the feedback circuit. The feedback circuit may be programmable and may be enabled to provide feedback or disabled to provide no feedback. Alternatively, the feedback circuit may always be enabled to provide feedback. In either case, the feedback circuit may have a variable gain to provide a variable input impedance for the amplifier.