| 摘要 |
A logarithmic amplifier (50) is provided with a calibration circuit (52) to allow for current measurement over a wide-dynamic range that includes extremely low current levels in a manner which mitigates or eliminates sensitivity to temperature. Calibration currents (IBias, IRef, Iboost) are generated by application of a series of voltage ramps of selectable slope to a capacitor (C2). This provides a set of known current levels selectable over a range of decades, for periodic calibration of the logarithmic amplifier (50). The selectable calibration currents can also be advantageously used to provide a fixed, known bias current to the input (-) of the logarithmic amplifier (50) to improve the response time of the amplifier (50) for measurement of small sensor currents (Isensor) on the order of 10-100 fA.
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