A nonlinear electronic device is often operated around a chosen steady operating point, or Q-point.

The operating point is found from the DC sources, surrounding circuit and nonlinear device relation. It specifies steady values such as transistor current and terminal voltages before any time-varying signal is added.

Biasing is the circuit design used to establish that point. For a transistor amplifier, the Q-point should keep the device inside the intended operating region while leaving enough voltage and current range for the signal to vary without driving the device into cutoff or another unwanted region.

The operating point is therefore not itself a gain or a small-signal approximation. It is the steady state about which later variations are analyzed.

Separating DC bias from signal variation makes nonlinear circuits easier to reason about: first establish where the device operates, then study how it responds to perturbations around that state.