| 摘要 |
A gain stage circuit having automatic level control is provided. In particular, the gain stage circuit provides an output voltage signal that is a predetermined multiple of the input voltage signal when the input voltage is less than a predetermined threshold. Moreover, the gain stage circuit provides an output voltage that is maintained at a constant predetermined level and independent of the input voltage signal for input voltages that are above a predetermined threshold. The gain stage circuit includes a rectification circuit, a variable gain stage circuit, a current switch and an operational amplifier. The current switch circuit of the present invention provides either an output current of the rectification circuit or a constant current to a reference input of the variable gain stage circuit. Moreover, the variable gain circuit includes a gain input that is coupled to receive a constant reference current.
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