Apparatus and methods sense or measure an input current, such as a current
indicating a logic state of a memory cell. A sensing circuit includes an amplifier,
a capacitor, a current source circuit, a clocked comparator and a clocked counter.
The current source circuit operates responsive to an output of the comparator to
supply or withdraw current to and from the capacitor during respective charging
and discharging intervals. The count in the clocked counter results from periodic
comparisons of the capacitor voltage with a reference voltage and is, therefore,
related to the logic state of the memory cell. The magnitude of current supplied
during charging is less than the magnitude withdrawn during discharging, allowing
use of a smaller counter.