Floating gate comparator with automatic offset manipulation functionality

We present a novel voltage comparator that uses nonvolatile floating gate charge storage for either offset nulling or automatic programming of a desired offset. We demonstrate the ability to reduce the variance of the initial offset and to accurately program a desired offset. We exploit the negative feedback functionality of pFET hot-electron injection to achieve fully automatic offset cancellation. The design has been fabricated in a commercially available 0.35μm process. Experimental results confirm the ability to reduce the variance of the initial offset by 2 to 3 orders of magnitude and to accurately define a desired offset with maximum observed deviation of 728μV and typical deviation 109μV. We achieve adaptation with settling time of 50ms, which is inversely proportional to the exponential of the injection voltage. We achieve controlled injection to accurately program the input offset to voltages uniformly distributed from -1V to 1V. The comparator exhibits a 5ns propagation delay.