Following are conceptual diagrams of electricity flowing through a junction field effect transistor (JFET). The JFET normally allows electricity to flow through. When pulsed, it closes the gap and impedes the flow. Analog or Digital In an analog application, the JFET serves as an amplifier. As a continuously variable voltage is applied to the gate, an analogous, but larger voltage, flows from source to drain. In a digital application, the JFET becomes an on/off switch. When the gate is pulsed, the switch changes its state from on to off. See transistor, n-type silicon, Boolean logic and FET.