Electrometer with wide dynamic range and fast response

摘要

A method and apparatus for measuring current includes sensing a first voltage at the output of an amplifier and calculating a current based on the first voltage and the resistance of a first resistance element that is electrically connected to an inverting input of the amplifier and the output of the amplifier is when the first voltage is below a predetermined level. The method also includes sensing a second voltage at the output of a buffer and calculating a current based on the first and second voltages and the resistance of the first resistance element and a second resistance element electrically connected to the inverting input of the amplifier and an input of the buffer and is also electrically connected to the output of the amplifier via at least one diode if the voltage output from the amplifier is above the predetermined level.