Current-voltage characteristic
The current-voltage characteristic curve (also called IU characteristic , current-voltage curve or also called UI diagram ) describes the relationship between electrical current and voltage in two-pole electrical components such as resistors , solar cells , accumulators and diodes .
In the case of ion channels , the current-voltage curve describes the relationship between membrane potential (or holding potential) and current through the membrane (in the case of whole-cell recordings) or the ion channel (in the case of single-channel measurements), see patch clamp .
Basics
According to Thévenin's theorem , any system of voltage sources and (complex) resistances can be modeled as a two-pole electrical component. It is therefore also possible to record current-voltage characteristics of more complex assemblies.
In the simplest case, the characteristic curve is linear, especially if the internal resistance of the element is an ohmic resistance . This is the case, for example, when an ideal voltage source is connected in series with a resistor.
In the case of semiconductors such as the ideal diode, however, a curved, non-linear characteristic is desired. Even non-ideal voltage sources behave nonlinearly to varying degrees.
If the straight line and the characteristic curve are only intersected once, one speaks of open-circuit voltage and of short-circuit current .
Measurement method
Basically, the same characteristic can be determined in two ways:
- In the potentiostatic case, an initial voltage is applied to the electrodes at one point in time . The applied voltage is then gradually increased until the final voltage is reached .
- In the galvanostatic case, a current is excited, which is then gradually increased until the final current is reached.
These measurement methods are used, among other things, in analog signature analysis , a test method from electronics manufacturing and repair.