A method of analyzing a molecule is disclosed. A voltage source is selectively connected to or disconnected from a capacitor using a switch controlled by a reset signal. A charge is stored in a capacitor when the voltage source is connected to the capacitor. The capacitor is discharged through a nanopore in a membrane when the voltage source is disconnected from the capacitor. A duty cycle of the reset signal is determined such that the voltage source and the capacitor is connected for at least a one tenth portion of a reset signal period and disconnected for a remaining portion of the reset signal period, such that a voltage across the nanopore is maintained at a higher level during the portion of the reset signal period in which the connection is maintained than during the remaining portion of the reset signal period in which the connection is not maintained.