Input offset voltage

The offset voltage is a characteristic size of operational amplifiers as a result of systematic errors in a circuit. The offset voltage measured at an output voltage of zero volts as a differential input voltage.

This zero point error is caused by base or gate currents of 3 fA to 200 nA, which flow through the input resistors, as well as production-related asymmetries of symmetrically structured input stages in the integrated circuit. When measuring amplifiers, which also process direct components, a DC compensation must be performed by an external circuit to compensate for the offset voltage and offset currents that occur through the same size, opposite directed currents. Only in this way, even the smallest potential differences can be measured accurately. In many operational amplifiers connections are brought out for balancing or zero point compensation.

The setting of the compensation point should be made at the working temperature. A long-term drift may be reduced by an artificial aging of the components at about 75 ° C ambient temperature over an operating time of 250 hours.