Importance

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Abstract

A data independent AGC control circuit for telecommunication applications is provided and includes an AGC amplifier, a fixed gain amplifier, a capacitor, and first, second, and third control circuits. The AGC amplifier has a data input, a control input, and a data output. The capacitor is coupled to the control input, and the charge on the capacitor effectively controls the gain of the AGC amplifier. The first control circuit is coupled to the data output of the fixed gain amplifier and to the capacitor and increases the stored charge on the capacitor when the data output exceeds a desired peak voltage level. The second control circuit is similarly coupled between the data output of the fixed gain amplifier and the capacitor, and decreases the stored charge on the capacitor when the data output exceeds a threshold voltage (typically 1/2 the desired peak voltage level). The third control circuit is coupled to the second control circuit and to the capacitor, and decreases the charge on the capacitor after the data output falls below the threshold voltage for a predetermined length of time. With the provided circuit, data values of zero will not trigger either the first or second control circuit, and the capacitor voltage and hence control voltage to the AGC amplifier will not change.

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First Claim