A single-stage amplifier circuit includes first and second transistors (e.g., BJTs or FETs) connected in parallel between the amplifier's input and output nodes. The first and second transistors are configured differently using known fabrication techniques such that a (first) cutoff frequency of the first transistor is at least 1.5 times greater than a (second) cutoff frequency of the second transistor, and such that a ratio of the respective cutoff frequencies produces a significant cancellation of second derivative transconductance (Gm″) in the amplifier output signal, whereby the amplifier achieves significantly improved IIP3. Alternatively, the amplifier is configured using MOSFETs having respective different channel lengths to achieve the desired cutoff frequency ratio. An exemplary communication circuit includes a low-noise amplifier having two NPN BJTs that are fabricated using different collector doping concentrations, different emitter doping concentrations, or different base region widths in order to achieve the desired cutoff frequency ratio.