Current measurement apparatus, molecular entity sensing apparatus, method of measuring a current, method of sensing a molecular entity

A method of measuring current, comprising:

• using a first charge amplifier to integrate a current to be measured;
• filtering an output from the first charge amplifier using a first low pass filter module and a second low pass filter module;
• and
• using a second charge amplifier to integrate a current derived from the filtered output from the first charge amplifier, wherein:
• the first charge amplifier is reset at the start of each of a plurality of sensing frames;
• at least a first sample of the output from the first charge amplifier is obtained in each sensing frame;
• and
• the sampling of the first sample alternates from one sensing frame to the next sensing frame between sampling via the first low pass filter module and sampling via the second lowpass filter module.

A method of measuring current, comprising:

• using a first charge amplifier to integrate a current to be measured;
• filtering an output from the first charge amplifier;
• and
• using a second charge amplifier to integrate a current derived from the filtered output from the first charge amplifier, wherein:
• the integration of the current by the first charge amplifier is performed simultaneously across a first capacitive element and a second capacitive element and the resetting of the first charge amplifier is performed by allowing a charge stored on the second capacitive element to flow onto and at least partially cancel a charge stored on the first capacitive element.

A method of measuring current, comprising:

• using a first charge amplifier to integrate a current to be measured;
• using a processing circuit to filter an output from the first charge amplifier;
• and
• using a second charge amplifier to integrate a current derived from the filtered output from the first charge amplifier, wherein:
• the processing circuit is configured such that information about the current to be measured propagates through the processing circuit from the first charge amplifier to the second charge amplifier as amounts of charge representing the current to be measured.