| 摘要 |
An automatic gain control circuit includes a gain controllable amplifier, a sampling circuit sampling the output of the amplifier, a rewritable memory storing a contrast digital value, an analog/digital converter converting the sampled signal into a digital signal, a comparator comparing the digital signal with the contrast digital value and producing a comparator output when the digital signal and the contrast digital value are a predetermined relationship, the memory changing the storing content with the digital signal as a new contrast digital value in response to the comparator output, a digital/analog converter converting the contrast digital value into an analog value to be applied to the amplifier to produce a constant level output from the amplifier. The automatic gain control circuit may include a first counter and a second counter to determine the attack time and the recovery time.
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