Dual-mode logarithmic amplifier having cascaded stages

Abstract

A dual-mode successive detection amplifier for providing a first output signal corresponding to a logarithmic function of a RF input signal, and for providing a second limited RF output signal is disclosed herein. A RF input signal is applied to the first of a succession of amplification stages arranged along a RF signal path to cascade amplify the RF input signal into the limited RF output signal. A plurality of detector/limiter (D/L) circuits interposed between the amplification stages limit RF signal energy propagating along the RF signal path so as to prevent saturation of the amplification stages. The D/L modules also provide a succession of detection signals corresponding to video envelopes of the RF signal energy produced by each of the amplification stages. The detection signals are applied to a video summation line and therein summed to produce the logarithmic output signal.