Operational amplifier with increased common mode input range
First Claim
Patent Images
1. An operational amplifier comprising:
- a first stage including;
a first differential transistor pair receiving a differential input signal at their gates, a first tail current source transistor connected to sources of the first differential transistor pair, and a load transistor pair connected in series with drains of the first differential transistor pair;
a second stage including a second differential transistor pair having gates connected to respective drains of the first differential transistor pair at their gates, and a second tail current transistor connected to sources of the second differential transistor pair; and
an output stage outputting a signal corresponding to the differential input signal, wherein substrates of the load transistor pair are connected to their respective sources, and wherein the first stage expands a common mode input range of the operational amplifier.
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Abstract
An operational amplifier includes a first stage with a first differential transistor pair inputting a differential input signal at their gates, a first tail current source transistor connected to sources of the first differential transistor pair, and a load transistor pair connected in series with the drain of first differential transistor pair. An input stage includes a second differential transistor pair connected to respective drains of the first differential transistor pair at their gates, and a second tail current transistor connected to sources of the differential transistor pair. An output stage outputs a signal corresponding to the differential input signal.
22 Citations
24 Claims
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1. An operational amplifier comprising:
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a first stage including;
a first differential transistor pair receiving a differential input signal at their gates, a first tail current source transistor connected to sources of the first differential transistor pair, and a load transistor pair connected in series with drains of the first differential transistor pair;
a second stage including a second differential transistor pair having gates connected to respective drains of the first differential transistor pair at their gates, and a second tail current transistor connected to sources of the second differential transistor pair; and
an output stage outputting a signal corresponding to the differential input signal, wherein substrates of the load transistor pair are connected to their respective sources, and wherein the first stage expands a common mode input range of the operational amplifier. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An operational amplifier comprising:
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a first stage inputting a differential input signal;
an input stage including a first differential transistor pair connected the first stage, and a first tail current source transistor connected to sources of the differential transistor pair; and
an output stage outputting a signal corresponding to the differential input signal, wherein the first stage expands a common mode input range of the operational amplifier, wherein the first stage includes;
a second differential transistor pair;
a second tail current source transistor connected to sources of the second differential transistor pair; and
a load transistor pair connected in series with drains of the second differential transistor pair, and wherein substrates of the load transistor pair are connected to their respective sources. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
a second differential transistor pair;
a current source connected to sources of the second differential transistor pair; and
a load transistor pair connected in series with the second differential transistor pair.
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20. An operational amplifier comprising:
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a first stage receiving a differential input signal;
means for inputting an input signal to a differential transistor pair;
means for outputting an amplified signal corresponding to the input signal; and
means for expanding a common mode input range of the means for inputting and the means for outputting, the means for expanding connected to the means for inputting, wherein a gain of the first stage is substantially constant within the common mode input range.
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21. An operational amplifier comprising:
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a first stage inputting an input signal and absorbing common mode variations in the input signal, and outputting a first differential signal;
an input stage including a differential transistor pair receiving the first differential signal from the first stage; and
an output stage connected to the input stage and outputting an amplified signal corresponding to the first differential signal, wherein a gain of the first stage is substantially constant within the common mode input range.
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22. An operational amplifier comprising:
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a first stage inputting a first differential input signal and outputting a second differential signal;
an input stage including a differential transistor pair receiving the second differential signal from the first stage; and
an output stage connected to the input stage and outputting an amplified signal corresponding to the second differential signal, wherein a common mode input range of the operational amplifier is larger than a common mode input range of the input stage and output stage alone, wherein a gain of the first stage is substantially constant within the common mode input range.
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23. An operational amplifier comprising:
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an input stage including;
a differential transistor pair inputting a differential input signal at their gates, a tail current source transistor connected to sources of the differential transistor pair, and a load transistor pair connected in series with drains of the differential transistor pair;
an amplifier connected to a gate of the tail current source transistor that permits the tail current source transistor to be squeezed; and
an output stage outputting a signal corresponding to the differential input signal.
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24. An operational amplifier comprising:
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means for inputting an input signal to a differential transistor pair, the means for inputting including;
a tail current source transistor connected to sources of the differential transistor pair;
means for squeezing the tail current source transistor;
means for outputting an amplified signal corresponding to the input signal; and
means for expanding a common mode input range of the input stage and the output stage, the means for expanding connected to the means for inputting, wherein a gain of the means for expanding and means for squeezing is substantially constant within the common mode input range.
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Specification