| 摘要 |
A dual-channel logarithmic amplifier for amplifying and detecting frequency components of an input signal comprising a plurality of frequency components and particularly for amplifying and detecting desired frequency components in the presence of high level, wide band noise. The inventive apparatus comprises a first amplifier means responsive only to a relatively narrow band of the frequency components comprising the input signal for amplifying desired frequency components in the narrow band and producing an output signal. Second amplifier means are provided responsive to a relatively wide band of the frequency components comprising the input signal including high level, wide band noise adjacent to the desired frequency components for amplifying the same. Negative feedback means are connected from the second amplifier means to the first amplifier means so as to reduce the input gain of the first amplifier means in response to the output from the second amplifier means. In this manner, the detection and amplification of small amplitude desired frequency components is made possible even in the presence of high level, wide band noise.
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