Switched-capacitor circuit analog-to-digital converter
First Claim
1. An amplifier circuit having input offset voltage compensation, comprising:
- an operational amplifier having an input and an output, the input being at an offset voltage level with respect to virtual ground;
first and second capacitors connected to the amplifier input;
first means for applying an input voltage signal level to the first capacitor to establish a voltage thereon equal to the input voltage minus the amplifier offset voltage, and for establishing the offset voltage level on the second capacitor;
second means for causing the voltage on the first capacitor to be transferred to the second capacitor, so as to be added to the offset voltage established thereon; and
third means for causing the voltage on the second capacitor to be transferred back to the first capacitor,whereby the operational amplifier produces an output voltage level functionally related to the input voltage signal level and independent of the amplifier input offset voltage.
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Accused Products
Abstract
A switched-capacitor analog-to-digital converter implements a conversion scheme involving execution of an algorithmic technique of successive-approximation comprising a number of iterations dependent upon the conversion resolution desired. The algorithm used requires analog processing to produce an output voltage that is two times the output voltage resolved to realize the previous bit. The "times two" function is realized by adding the voltage of the last iteration to itself (i.e., V+V=2V). This is accomplished by storing the output voltage resolved into the previous bit and separately storing a voltage corresponding to that voltage. Both stored voltages are then transferred to an integrator circuit which adds the two voltages and produces the output voltage to be resolved into the next bit.
43 Citations
22 Claims
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1. An amplifier circuit having input offset voltage compensation, comprising:
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an operational amplifier having an input and an output, the input being at an offset voltage level with respect to virtual ground; first and second capacitors connected to the amplifier input; first means for applying an input voltage signal level to the first capacitor to establish a voltage thereon equal to the input voltage minus the amplifier offset voltage, and for establishing the offset voltage level on the second capacitor; second means for causing the voltage on the first capacitor to be transferred to the second capacitor, so as to be added to the offset voltage established thereon; and third means for causing the voltage on the second capacitor to be transferred back to the first capacitor, whereby the operational amplifier produces an output voltage level functionally related to the input voltage signal level and independent of the amplifier input offset voltage. - View Dependent Claims (2, 3, 4)
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5. Apparatus for developing a voltage output level that is two times a previously existing output voltage level, comprising:
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an integrator circuit having an input and an output, for producing an output voltage level; first means connectable to the integrator circuit input, for receiving and storing a voltage corresponding to a previously existing output voltage level; second means for accessing the integrator circuit output to obtain the output voltage level, and for storing the same as a previously existing voltage level; third means for causing the voltage stored in said first means to be transferred to the integrator circuit; and fourth means for causing the voltage in said second means to be transferred to the integrator circuit and be added to the voltage transferred from said first means. - View Dependent Claims (6, 7, 9, 10)
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8. A switched-capacitor circuit for developing an output voltage level that is two times a previously existing output voltage level, comprising:
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an operational amplifier having an input and an output; an integrating capacitor connectable in a feedback loop between the amplifier input and output; a storage capacitor connected to the integrating capacitor, for storing a voltage corresponding to a previously existing amplifier output voltage level; means for accessing the amplifier output and storing the output voltage level as a previously existing amplifier output voltage level; means for causing the voltage on the storage capacitor to be transferred to the integrating capacitor; and means for causing the voltage in the voltage storing means to be transferred to the integrating capacitor and be added to voltage transferred from the storage capacitor.
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11. A switched-capacitor circuit for developing an output voltage level that is two times a previously existing output voltage level, comprising:
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an operational amplifier having an input and an output, said amplifier producing an output voltage level; a first capacitor connected to the amplifier input; a second capacitor connected to the amplifier input, for storing a voltage corresponding to a previously existing amplifier output voltage level; means for storing a voltage level applied thereto; a first switch for connecting the first capacitor in a feedback loop between the amplifier input and output; a second switch for connecting the second capacitor to ground potential; a third switch for connecting the voltage level storing means to the amplifier output to obtain and store the amplifier output voltage level as a previously existing voltage level; a fourth switch for connecting the voltage level storing means to the first capacitor; and means for controlling said switches to (i) cause the voltage stored on the second capacitor to be transferred to the first capacitor, (ii) cause the voltage stored in the voltage level storing means to be transferred to the first capacitor and be added to the voltage transferred from the second capacitor, and (iii) cause the amplifier to produce on output voltage corresponding to the voltage on the first capacitor. - View Dependent Claims (12)
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13. A switched-capacitor analog-to-digital converter, comprising:
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an operational amplifier integrator circuit having an input and an output, and including first and second capacitors connected to the amplifier input; said integrator circuit producing an output voltage level corresponding to the voltage on the first capacitor; means connectable to the integrator circuit output for resolving the integrator circuit output voltage level into a binary digit value, and providing an output signal indicative thereof; means connectable to the integrator circuit output for accessing and storing the resolved output voltage level; means for connecting the second capacitor in a feedback loop between the amplifier input and output, and for connecting the first capacitor between the amplifier input and ground, to cause the voltage on the first capacitor to be transferred to the second capacitor and stored thereon; means for connecting the first capacitor in a feedback loop between the amplifier input and output, and for connecting the second capacitor between the amplifier input and ground, to cause the voltage stored on the second capacitor to be transferred back to the first capacitor; means for connecting the output voltage level storing means to the integrator circuit, for causing the voltage stored therein to be transferred to the first capacitor and be added to the voltage transferred from the second capacitor; and means connected to the integrator circuit, for causing a reference voltage level, selectively of either polarity based upon the binary digit value produced by said resolving means, to be placed on the first capacitor along with voltages transferred from the second capacitor and the output voltage storing means. - View Dependent Claims (14, 15, 16, 17, 20)
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18. A switched-capacitor analog-to-digital converter, comprising:
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an operational amplifier having an input and an output; a first capacitor connected to the amplifier input; a second capacitor connected to the amplifier input, the second capacitor being of equal capacitance value to the first capacitor; a first switch connected to the first capacitor, for applying thereto an analog input voltage to be converted to a representative digital word; a second switch for connecting the first capacitor in a feedback loop between the amplifier input and output; a third switch for grounding the other lead of the first capacitor; a fourth switch for connecting the second capacitor in a feedback loop between the amplifier input and output; a fifth switch for grounding the other lead of the second capacitor; a comparator connectable to the amplifier output, for processing the voltage level available at the amplifier output to determine the polarity, and for producing an output signal of a binary digit value indicative of the determination; means connectable to the amplifier output, for accessing and storing the amplifier output voltage level received by the comparator; a sixth switch for connecting the voltage storing means to the first capacitor; means connected to the amplifier input for causing a reference voltage level selectively of either polarity based upon the result of the comparator determination to be integrated on the first capacitor; and means for actuating said switches in a predetermined sequence to cause (a) an amplifier output voltage level corresponding to the voltage on the first capacitor to be processed by the comparator and stored by the storing means, (b) the voltage on the first capacitor to be transferred to the second capacitor and stored thereon, (c) the voltage stored by the storing means to be transferred to the first capacitor, (d) the voltage stored on the second capacitor to be transferred back to the first capacitor and added to the voltage from the storing means, and (e) a reference voltage to be integrated on the first capacitor. - View Dependent Claims (19)
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21. A method of analog-to-digital conversion, comprising the steps of:
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(a) sampling an input analog voltage to be converted to a digital word of N binary digits; (b) storing the voltage sample on a first capacitor; (c) producing an output voltage corresponding to the voltage on the first capacitor; (d) determining the polarity of the output voltage and producing a binary signal indicative thereof; (e) storing the output voltage; (f) transferring the voltage on the first capacitor to a second capacitor; (g) transferring the stored output voltage to the first capacitor; (h) transferring the voltage on the second capacitor back to the first capacitor for addition to the voltage thereon; (i) causing a reference voltage of a polarity dependent upon the value of said binary signal to be integrated onto the first capacitor; and (j) repeating steps (c) through (i) N-1 times.
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22. A method of developing a voltage that is two times a previously existing voltage, comprising the steps of:
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establishing a voltage on a first capacitor; producing an output voltage corresponding to the voltage on the first capacitor; storing the output voltage; transferring the voltage on the first capacitor to a second capacitor; transferring the stored output voltage to the first capacitor; and transferring the voltage on the second capacitor back to the first capacitor for addition to the voltage thereon.
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Specification