Automatic measurement circuit for MOS structures - determines voltage threshold as function of substrate polarisation using two operational amplifiers

摘要

The automatic measurement circuit determines the voltage threshold of an MOS structure as a function of the substrate polarisation. The MOS structure is kept in a state of saturation so that the drain current is constant. The voltage difference between the grid and source electrodes is then measured using an operational amplifier (7), this representing the threshold voltage of the MOS structure. Saturation is maintained by an operational amplifier (2) whose non-inverting input is connected to the drain electrode (D) of the MOS structure and also to a constant current generator (3), while its inverting input is connected to the source electrode (5) via a resistance (5) and to another constant current generator (4). The amplifier's output is connected to the grid electrode (6). The substrate electrode is earthed.