Monolithic programmable gain-integrator stage
First Claim
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1. An electronic gain-integrator stage having an input terminal for receiving an input signal and having an output terminal, comprising:
- M operational amplifier gain stages connected in series where M is a selected integer varying from 1 to K, where K is the maximum number of gain stages, said M operational amplifier gain stages each having a programmable gain and an inherent offset voltage and said Mth gain stage having an output lead which provides an output signal which includes an error component which is a function of said offset voltages of said M operational amplifier gain stages;
an operational amplifier integrator stage connected to said gain stages, having an inherent offset voltage, and includingmeans for integrating during the first half of a selected cycle the negative of said error component, which is produced in response to the initialization of said M gain stages, and integrating during the second half of said selected cycle both the positive of said error component, which is produced in response to said input signal, and the positive of said input signal multiplied by each of said programmable gains of each of said M gain stages;
wherein the negative of said error component is integrated once for each integration of the input signal, whereby the effects of said offset voltages of each of said M gain stages are eliminated.
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Abstract
A switched capacitor gain stage (110, 120) having a programmable gain factor. This gain factor is determined by the connection of desired gain determining components (14-17; 25-28) contained within a component array (100, 101). A sample and hold circuit (46) is provided for the storage of the error voltage of the entire gain-integrator stage. This stored error voltage (Verror) is inverted and integrated one time for each integration of the input voltage (Vin), thus eliminating the effects of the inherent offset voltages of the circuit from the output voltage (Vout).
112 Citations
10 Claims
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1. An electronic gain-integrator stage having an input terminal for receiving an input signal and having an output terminal, comprising:
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M operational amplifier gain stages connected in series where M is a selected integer varying from 1 to K, where K is the maximum number of gain stages, said M operational amplifier gain stages each having a programmable gain and an inherent offset voltage and said Mth gain stage having an output lead which provides an output signal which includes an error component which is a function of said offset voltages of said M operational amplifier gain stages; an operational amplifier integrator stage connected to said gain stages, having an inherent offset voltage, and including means for integrating during the first half of a selected cycle the negative of said error component, which is produced in response to the initialization of said M gain stages, and integrating during the second half of said selected cycle both the positive of said error component, which is produced in response to said input signal, and the positive of said input signal multiplied by each of said programmable gains of each of said M gain stages; wherein the negative of said error component is integrated once for each integration of the input signal, whereby the effects of said offset voltages of each of said M gain stages are eliminated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. The method of eliminating the effects of the offset voltages of a gain-integrator stage which includes an operational amplifier integrator stage and a plurality of operational amplifier gain stages, where M is a selected positive integer, which comprises the steps of:
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initializing said operational amplifier integrator stage, thereby producing an inherent offset voltage; initializing said M operational amplifier gain stages, thereby producing a first output signal, which is a function of the inherent offset voltages of each operational amplifier gain stage; storing said first output signal minus said offset voltage of said operational amplifier integrator stage on an input capacitor; storing the negative of said offset voltage of said operational amplifier integrator stage on said input capacitor, thereby integrating the negative of said first output signal of said operational amplifier gain stages and eliminating the effects of said offset voltage of said operational amplifier integrator stage; storing said offset voltage of said operational amplifier integrator stage on said input capacitor; applying an input signal to said operational amplifier gain stages, thereby producing a second output signal which is a function of said offset voltages of said operational amplifier gain stages, of said input signal, and the gain of each said operational amplifier gain stage; and storing on said input capacitor of said second output signal minus said offset voltage of said operational amplifier integrator stage, thereby integrating said second output signal on said integrating capacitor and eliminating the effects of said offset voltage of said operational amplifier integrator stage, thereby eliminating the effects of said offset voltage of operational amplifier gain stages.
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Specification