Switch transistors, such as for example power metal oxide semiconductor field effect transistors (power MOSFETs) or insulated gate bipolar transistors (IGBTs), may be used in power electronics. These transistors require almost no gate current in the ON-state (or conducting state). Such power transistors are usually driven with low-ohmic (or low impedance) drivers (for example voltage sources) to achieve short switching times in order to keep switching power losses low.
Further, power transistors which have a gate-source characteristic similar to that of a pn-junction may be used. Examples of such transistors include junction field effect transistors (Junction-FETs) and high electron mobility transistors (HEMTs). Examples of junction field effect transistors may include transistors with wide bandgap material such as for example silicon carbide (SiC) transistors. Examples of high electron mobility transistors may include transistors with wide bandgap material such as for example gallium nitride (GaN) transistors. In case such power transistors are driven by a voltage source, variations in the voltage of the voltage source and in the input characteristic of the transistor, for example due to temperature variation or parameter variation, may result in a substantial change in the operating point of the transistor, which is usually undesired. Ideally, such transistors would be operated in their ON-states using a low constant current. For switching from the OFF-state (or non-conducting state) to the ON-state, a low ohmic resistance driving is desired to achieve short switching times in order to keep switching power losses low. It would be desirable to provide such a driver circuit for the operation of these transistors.