In a field-effect transistor, what circuit parameter change causes the current to increase?

In a junction field-effect transistor (JFET), the gate-source junction is normally reverse-biased. This reverse bias creates a depletion region that "pinches" the channel, restricting the flow of current between the source and the drain. When this reverse bias voltage is decreased (meaning the voltage is moved closer to zero), the depletion region shrinks. This widens the conductive channel, allowing more current to flow through the device. Applying or increasing a forward bias is generally avoided in a JFET because it would cause the gate to conduct current, destroying its high input impedance characteristics. Therefore, current is increased by decreasing the reverse bias.