Lastlinie

Lastlinie is a German term primarily used in electrical engineering to denote the load line of an electrical circuit. The load line represents the relationship between current and voltage imposed by the external circuit—the power source and the load—and is used together with the device’s current–voltage characteristics to determine the operating point of the active element.

In a common-emitter transistor circuit with a fixed supply voltage Vcc and a collector resistor Rc, the load line can be described by the equation Ic = (Vcc − Vce)/Rc. This line intersects the Ic axis at Ic = Vcc/Rc (when Vce = 0) and the Vce axis at Vce = Vcc (when Ic = 0). The slope of the load line is −1/Rc. By plotting the transistor’s output characteristics on the same graph, the intersection defines the quiescent operating point (Q-point). The load line concept likewise applies to other devices, such as MOSFETs or vacuum tubes, with the appropriate device characteristics.

The load line is a fundamental tool for biasing and designing amplifiers. It helps engineers assess headroom, linearity, and distortion, and it guides adjustments to component values or supply voltages to achieve a desired operating region and signal swing.

Outside of electronics, Lastlinie is not a standard technical term; in German-language contexts its primary meaning remains the load line in circuit analysis. See also load-line analysis, I–V characteristics, and transistor biasing.