On a transistor output characteristic family, the two endpoints of the DC load line correspond to which operating conditions of the device?

Introduction:
The DC load line graphically represents all possible operating points (I_C, V_CE) for a given supply and load on a transistor's output characteristic curves. Understanding its endpoints is crucial for biasing, allowable signal swing, and avoiding distortion in amplifiers or achieving robust switching in digital applications.

Given Data / Assumptions:

• Fixed supply voltage V_CC and collector load resistor R_C.
• Transistor plotted with I_C vs. V_CE characteristics.
• Static (DC) analysis; no AC signal applied when drawing the line.

Concept / Approach:
The load line is defined by V_CE + I_C * R_C = V_CC. When I_C = 0, V_CE = V_CC (cutoff). When V_CE ≈ 0, I_C ≈ V_CC / R_C (saturation). These two intercepts are the physical extremes; every practical quiescent point (Q-point) lies somewhere between them when the device conducts linearly.

Step-by-Step Solution:

Verification / Alternative check:
Plotting the line on the characteristic family shows it intersecting the axes at the cutoff and saturation corners. Simulations or bench measurements (varying base drive) move the Q-point along this line, confirming the endpoint interpretations.

Why Other Options Are Wrong:

• the operating point: The Q-point is one chosen point on the line, not an endpoint.
• the power curve: Power contours are separate overlays, not the load line ends.
• the amplification factor: A small-signal parameter, not indicated by the intercepts.

Common Pitfalls:
Confusing AC load lines with DC, or mislabeling the intercepts. Remember cutoff at I_C = 0 and saturation at V_CE ≈ 0.

Final Answer:
saturation and cutoff