Amplifier device for amplifying small currents

An amplifier device for receiving currents, comprising

• a first current path adapted to measure small input currents of less than 100 pA when said input current flows through said first current path,
• an input amplifier device included in the first current path, comprising
• at least one first amplifier,
• an output,
• an inverting input,
• a first feedback path connecting the output to the inverting input, and
• a feedback element included in the first feedback path,
• wherein the first amplifier comprises at least one protective element in the first current path,
• a second current path adapted to measure larger input currents when said input current flows through said second current path with a maximum input current of at least 10 times the input current to be received in the first current path, said second current path being at least partially different from said first current path,
• wherein, at least one of the protective elements of the input amplifier device in the first current path is also part of the second current path such that when a measuring range changes from a range for measuring small input currents in the first current path to a range for measuring large input currents in the second current path, the input current flows through the at least one protective element comprised in the first and second current paths.