A high-linear amplifier receives, from an input bandpass filter, input signals including weak process signals and strong interference signals, amplifies the input signals, and transmits the amplified signals to an output bandpass filter. The high-linear amplifier includes a transistor and a feedback circuit that stabilizes the operating current of the transistor. The operating current includes the direct-current and low-frequency output signal currents of the transistor. The feedback circuit includes an interference detector that rectifies a portion of the high-frequency output signals of the transistor and extends the linear range of the high-linear amplifier. An interference indicator unit alerts an operator to the presence of excessively high levels of interference before the high-linear amplifier enters the non-linear mode. Amplified signals rejected by the output bandpass filter are reflected back to the high-linear amplifier stage. A directional coupler prevents the reflected signals from disrupting the operation of the interference detector.