A gated metal oxide semiconductor field effect transistor (MOSFET) gain cell is formed with a flow channel for molecule flow. The flow channel is formed under the gate, and between a source and drain of the transistor. The molecule flow modulates a gain of the transistor. Current flowing between the source and drain is representative of charges on the molecules flowing through the flow channel. A plurality of individually addressable gain cells are coupled between chambers containing samples to measure charges on molecules in the samples passing through the gain cells.