Inngangsbiasstrømmen

Inngangsbiasstrømmen, also known as input bias current, is a parameter associated with operational amplifiers (op-amps) and other electronic devices. It represents the small amount of DC current that flows into the input terminals of the device. This current is necessary to bias the internal transistors of the op-amp into their active region.

The magnitude of inngangsbiasstrømmen is typically very small, often in the nanoampere (nA) or picoampere (pA) range. However, even this small current can have significant effects in sensitive circuits, especially those with high input impedances or long signal paths. When inngangsbiasstrømmen flows through a resistor at the op-amp's input, it creates a voltage drop. If the bias currents into the two input terminals are not well-matched, this can lead to an output offset voltage, even when no input signal is present. This offset voltage can be undesirable in precision measurement applications.

Factors influencing inngangsbiasstrømmen include the type of semiconductor technology used in the op-amp's construction. Bipolar junction transistor (BJT) input op-amps generally have larger bias currents than field-effect transistor (FET) input op-amps. FET input op-amps, such as JFET or MOSFET input types, exhibit significantly lower input bias currents, making them suitable for applications requiring very high input impedance. When selecting an op-amp for a particular circuit, it is important to consider the magnitude of the inngangsbiasstrømmen and its potential impact on the overall circuit performance. Techniques like using compensating resistors in the feedback network can help minimize the effects of inngangsbiasstrømmen.