IGBT stands for Insulated Gate Bipolar Transistor. These devices are most typically used in applications switching high voltages, up to several kilovolts. MOSFETs and IGBTs are alternatives in many applications, but for higher voltage applications, IGBTs currently stand alone, as well as dominating in low frequency applications above 250 V. Like MOSFETs, IGBTs have an insulated gate, making them easier to drive than ordinary bipolar transistors. IGBT devices have a parasitic capacitance between the collector and the gate known as Miller capacitance. Essentially, when IGBTs are connected in cascaded configurations typical to half-bridge or full bridge power circuits, as the upper IGBT is switched on, a voltage develops through the Miller capacitance of the lower IGBT that can bias it to an ON state which is potentially dangerous and destructive. The same effect is seen in the upper IGBT when the lower IGBT is switched on. Another issue arises when high currents are switched off by the IGBT; stray inductance causes a negative voltage to appear at the emitter which can have sufficient magnitude to bias the IGBT back to an ON state. A common technique used in order to prevent spurious turn-on from either of these effects is to use a negative gate drive to turn off the IGBTs. A negative gate bias has the additional feature of providing faster turn-off, to reduce switching losses. Therefore, in many applications it is desirable that the gate drive circuit have a positive voltage to bias the gate ON and negative voltage to turn it off. The specific voltage for the positive bias varies by IGBT manufacturer, model, and application, but typically cannot exceed 20-30 V, as voltages in excess of this can damage the gate. Other considerations keep designers from approaching this limit as the short circuit survival time decreases with increasing gate voltage. The gate voltage must also exceed a minimum level of about 3-10 V to turn the device on, but higher voltages drive faster turn-on that consequently achieves more efficient switching. As a result of these considerations, values for the positive bias typically fall between 15 and 20 V. The negative gate bias value is also a compromise of multiple factors, but is generally in the range of -5 to -15 V.