Comparators are the basic building blocks for many circuits such as analog to digital converters, semiconductor memories and PLLs. As is known in the art, a comparator compares the input voltage with a reference voltage and switches its output to indicate the higher voltage. A comparator circuit typically comprises an input pair of voltage controlled switches such as transistors driven by an input voltage driver and a corresponding reference voltage input pair of voltage controlled switches such as transistors driven by a reference voltage driver.
However, when the comparator starts latching an input, there is a large voltage variation across the source and drain voltage controlled switches. This variation in voltage is “kicked back” to the input of the comparator through parasitic, i.e., coupling capacitances of said switches. Also as the input voltage driver or reference voltage driver do not have zero output impedance, the input voltage of the comparator changes and the accuracy of the comparator reduces.