To reduce the pixel size to the smallest dimensions and simplest form of operation, a pixel may be formed by using only one ion sensitive field-effect transistor (ISFET). This one-transistor, or 1T, pixel can provide gain by converting the drain current to voltage in the column. Configurable pixels can be created to allow both common source read out as well as source follower read out. A plurality of the 1T pixels may form an array, having a number of rows and a number of columns and a column readout circuit in each column. A cascoded device enabled during readout may be used to provide increased programmable gain.