Offset voltage
The offset voltage (more precisely: input offset voltage) is a characteristic of operational amplifiers as a result of inevitable systematic errors in the circuit and the components used. The input offset voltage is the necessary differential input voltage for an output voltage of 0 volts. It depends on the temperature and the input voltage itself and is also subject to long-term drift due to aging processes.
This zero point error has several sources: On the one hand, one component arises from the not exactly symmetrical and temperature-compensated structure of the IC; on the other hand, another component arises from the not exactly symmetrical wiring of the inverting and the non-inverting input through input currents, which usually range from nano to Pico amperes for bipolar transistors and in the range of femto amps (e.g. 3 fA) for field effect transistors . With measuring amplifiers that also have DC componentsprocess, a DC voltage compensation must be carried out by an external circuit in order to compensate the offset voltage or the occurring offset currents with equally large, oppositely directed currents. Only then can even the smallest potential differences be measured precisely. In many operational amplifiers, connections for balancing or zero point compensation are brought out.
The compensation point should be set at working temperature. Long-term drift can be reduced by artificial aging of the components at the upper end of the permitted temperature range over an operating time of several hundred hours.
Individual evidence
- ↑ Data sheet LMP7721 from March 14, 2008
literature
- Dieter Nührmann: work book electronics . Franzis-Verlag, Munich 1984, ISBN 3-7723-6544-2 , p. 817 .
- U Tietze, C Schenk: Semiconductor circuit technology . 9th edition. Springer-Verlag, ISBN 3-540-19475-4 , pp. 124 .