Sampled data automatic gain control
First Claim
1. Apparatus for automatically controlling the gain of an amplifier having an input terminal for receiving an input signal of varying amplitude, an output terminal for providing an output voltage, and a control terminal for receiving a control voltage operable to control said gain, said apparatus comprising:
- means for providing an error voltage indicative of a difference between said output voltage of said amplifier and a desired target voltage;
counting means, coupled to said amplifier control terminal, for generating digital words;
means for generating a plurality of voltage levels within a predetermined time interval with each said voltage level indicative of an associated digital word;
comparison means for comparing said plurality of voltage levels with said error voltage and for providing a control signal when said error voltage is within a predetermined range of any of said voltage levels; and
means responsive to said control signal for providing said control voltage to said amplifier in accordance with said digital word whereby said gain is updated, and wherein said means responsive to said control signal is operable to terminate said counting and said generating of said voltage levels.
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Accused Products
Abstract
An amplifier circuit employing automatic gain control (AGC), with the gain responsive to a varying input signal level, and particularly adapted for manufacture as an integrated circuit. In a preferred embodiment, an error voltage is produced which is indicative of the difference between the RMS output voltage of the amplifier and a target RMS voltage. A ramp generator generates a ramp voltage in accordance with a digital count generated by a ripple counter. A comparator then produces a control signal in accordance with the difference between the ramp voltage and the error voltage. When the control signal is indicative of the amplifier output voltage differing from the target voltage, the gain is updated in accordance with the digital count and the count and ramp voltage are reset.
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Citations
20 Claims
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1. Apparatus for automatically controlling the gain of an amplifier having an input terminal for receiving an input signal of varying amplitude, an output terminal for providing an output voltage, and a control terminal for receiving a control voltage operable to control said gain, said apparatus comprising:
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means for providing an error voltage indicative of a difference between said output voltage of said amplifier and a desired target voltage; counting means, coupled to said amplifier control terminal, for generating digital words; means for generating a plurality of voltage levels within a predetermined time interval with each said voltage level indicative of an associated digital word; comparison means for comparing said plurality of voltage levels with said error voltage and for providing a control signal when said error voltage is within a predetermined range of any of said voltage levels; and means responsive to said control signal for providing said control voltage to said amplifier in accordance with said digital word whereby said gain is updated, and wherein said means responsive to said control signal is operable to terminate said counting and said generating of said voltage levels. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. Apparatus for amplifying an input signal of varying amplitude to produce an output signal, comprising:
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range control means for providing a digital control word indicative of an amplitude range that said input signal is within; preamplification means, coupled to said range control means, for amplifying said input signal at a gain corresponding to said digital control word to produce an intermediate amplified signal; an output amplifier having an input terminal for receiving said intermediate amplified signal, an output terminal for providing said output signal, and a control terminal for receiving a control voltage operable to control said gain; means for providing an error voltage indicative of a difference between said output signal and a desired target voltage; counting means for generating digital words; means for generating a plurality of voltage levels within a predetermined time interval with each said voltage level indicative of an associated digital word; comparison means for comparing said plurality of voltage levels with said error voltage and for providing a control signal when said error voltage is within a predetermined range of any of said voltage levels; and means responsive to said control signal for providing said control voltage to said amplifier in accordance with said digital word whereby said gain is updated to provide said output signal at a substantially constant RMS amplitude, and wherein said means responsive to said control signal is operable to terminate said counting and said generating of said voltage levels. - View Dependent Claims (17, 18)
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19. Method for automatically controlling gain of an amplifier producing an output signal in response to a varying input signal level to said amplifier, comprising the steps of:
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providing an error voltage indicative of a difference between said output signal of said amplifier and a desired target voltage; generating a digital count; generating a plurality of voltage levels according to said digital count; providing a control signal in accordance with the difference between said voltage levels and said error voltage; and updating the gain of said amplifier, responsive to said control signal, to a value corresponding to said digital count. - View Dependent Claims (20)
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Specification