| 摘要 |
A resolution enhancer circuit provides an increased resolution capability for an A/D converter. The resolution enhancer circuit receives as input an analog input signal having a range greater than the effective range of the A/D, and prescales the input signal to a range that is within the common mode range of op amps used within the resolution enhancer circuit. The input signal can also have a range much less than the effective range of the A/D, and then it would be increased by the prescaler to be within an operable range of the A/D. The prescaled signal is provided to a sampling circuit, which samples the prescaled signal at times determined to be near-saturation conditions of the A/D. A magnified difference between the prescaled signal and the sampled signal, biased to the sampled signal, is then input to the A/D, which determines a number of A/D counts based on that value. As the input signal varies, the number of A/D counts may approach either a high or low saturation condition, which causes a resampling of the prescaled signal. This resampling of the prescaled signal effectively moves the approximate center of a high resolution window to a current value of the analog input signal, and allows for an n-bit A/D to provide increased resolution for a wide ranging analog input signal.
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