DC feedback circuit using sample and hold circuits
First Claim
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1. An operational amplifier having an input and an output and circuitry for preventing a DC level shifting and saturation of said operational amplifier in response to the concurrent reception by said input of an AC signal and a DC offset, said operational amplifier circuitry comprising:
- circuitry connected to said output and controlled by circuitry responsive to said reception of said AC signal and independent of said operational amplifier for storing the amplitude of positive and negative signal peaks appearing on said output in response to the reception of an AC signal on said input,means for generating a feedback signal representing the averaged amplitude of said positive and negative signal peaks, andmeans for applying at least a portion of said feedback signal to said input that receives said AC signal to cancel any DC offset of said AC signal on said input.
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Abstract
Sample and hold circuits are used to detect a DC component of an AC signal on an amplifier'"'"'s output to generate a feedback signal that is applied to the amplifier'"'"'s input to cancel out a DC component of an AC input signal. The sample and hold circuits detect the peak excursions of the AC output signal and apply the stored peaks to averaging circuitry which determines the magnitude of the DC component of the output signal.
16 Citations
40 Claims
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1. An operational amplifier having an input and an output and circuitry for preventing a DC level shifting and saturation of said operational amplifier in response to the concurrent reception by said input of an AC signal and a DC offset, said operational amplifier circuitry comprising:
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circuitry connected to said output and controlled by circuitry responsive to said reception of said AC signal and independent of said operational amplifier for storing the amplitude of positive and negative signal peaks appearing on said output in response to the reception of an AC signal on said input, means for generating a feedback signal representing the averaged amplitude of said positive and negative signal peaks, and means for applying at least a portion of said feedback signal to said input that receives said AC signal to cancel any DC offset of said AC signal on said input. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An operational amplifier having an input and an output and circuitry for preventing a DC level shifting and saturation of said operational amplifier in response to the reception by said input of an AC signal having a DC offset, said operational amplifier circuitry comprising:
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a first storage circuit connected to said output and controlled by circuitry independent of said operational amplifier and operable in response to the receipt of said AC signal for storing the peak amplitude of positive signals appearing on said output in response to the reception of signals of a first polarity on said input, a second storage circuit connected to said output and controlled by circuitry independent of said operational amplifier and operable in response to the receipt of said AC signal for storing the peak amplitude of negative signals appearing on said output in response to the reception of signals of a second polarity on said input, means for generating a feedback signal representing the averaged peak amplitude of said signals stored by said first and second storage circuits, and means for applying at least a portion of sad feedback signal to said input that receives said AC signal to cancel any DC offset of an AC signal applied to said input. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. An operational amplifier having an input and an output and circuitry for preventing a DC level shifting and saturation of said operational amplifier in response to the reception by said input of an AC signal having a DC offset, said operational amplifier circuitry comprising:
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a first sample and hold circuit connected to said output, means independent of said operational amplifier and responsive to transitions of a first polarity of said AC signal for operating said first sample and hold circuit to store the peak amplitude of signals of a positive polarity appearing on said output, a second sample and hold circuit connected to said output, means independent of said operational amplifier and responsive to transitions of a second polarity of said AC signal for operating said second sample and hold circuit to store the peak amplitude of signals of a negative polarity appearing on said output, a voltage divider connected between an output of said first sample and hold circuit and an output of said second sample and hold circuit, a tap on said voltage divider, said first and second sample and hold circuits being effective to apply a potential across said voltage divider so that the potential of said tap represents the averaged value of said signals stored in said first and second sample and hold circuits, and means for applying at least a portion of said potential on said tap to said input of said operational amplifier that receives said AC signal to cancel any DC component of said AC signal applied to said input of said operational amplifier. - View Dependent Claims (18, 19, 20)
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21. A method of operating an operational amplifier having an input and an output and circuitry for preventing a DC level shifting and saturation of said operational amplifier in response to the concurrent reception by said input of an AC signal and a DC offset, said method comprising the steps of:
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operating circuitry independent of said operational amplifier and responsive to the receipt of said AC signal for storing the peak of positive and negative signals appearing on said output in response to the reception of an AC signal on said input, generating a feedback signal representing the averaged peak amplitude of said positive and negative signals, and applying at least a portion of said feedback signal to said input that receives said AC signal to cancel any DC component of said AC signal on said input. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
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29. A method of operating an operational amplifier having an input and an output and circuitry for preventing a DC level shifting and saturation of said operational amplifier in response to the reception by said input of an AC signal having a DC offset, said method comprising the steps of:
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receiving an AC signal having a DC component on an input of said operational amplifier, operating a first storage circuit connected to an output of said operational amplifier under control of a circuit independent of said operational amplifier and responsive to the reception of said AC signal for storing the peak amplitude of positive signals appearing on said output in response to the reception of signals of a first polarity on said input, operating a second storage circuit connected to said output under control of a circuit independent of said operational amplifier and responsive to the reception of said AC signal for storing the peak amplitude of negative signals appearing on said output in response to the reception of signals of a second polarity on said input, generating a feedback signal representing the averaged amplitude of said signals stored by said first and second storage circuits, and applying at least a portion of said feedback signal to said input that receives said AC signal to cancel any DC component of an AC signal applied to said input. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36)
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37. A method of operating an operational amplifier having an input and an output and circuitry for preventing a DC level shifting and saturation of said operational amplifier in response to the reception by said input of an AC signal having a DC offset, said method comprising the steps of:
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operating a first sample and hold circuit under control of circuitry responsive to said reception of said AC signal and independent of said operational amplifier to store the peak amplitude of positive signals appearing on said output in response to transitions of a first polarity of an AC signal on said input, operating a second sample and hold circuit under control of circuitry responsive to said reception of said AC signal and independent of said operational amplifier to store the peak amplitude of negative signals appearing on said output in response to transitions of a second polarity of said AC signal on said input, operating said first and second sample and hold circuits for applying a potential across a voltage divider connected between an output of said first sample and hold circuit and an output of said second sample and hold circuit so that the potential of a tap on said voltage divider represents the averaged value of said signals stored in said first and second sample and hold circuits, and applying at least a portion of said potential on said tap to said input of said integrating operational amplifier that receives said AC signal to cancel any DC component of said AC signal applied to said input of said operational amplifier. - View Dependent Claims (38, 39, 40)
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Specification