Assertion–Reason on large-signal analysis: For large signal variations an amplifier circuit must often be analysed graphically because the transistor output characteristics are nonlinear. Evaluate the statements.

Introduction / Context:
Amplifier analysis can be categorized as small-signal (around a bias point) or large-signal (where the device traverses a wide portion of its characteristics). This question examines why graphical methods such as load-line analysis are used for large-signal cases.

Given Data / Assumptions:

• Transistor output characteristics are inherently nonlinear outside a very small region.
• Large excursions drive the operating point across curved portions of the characteristics.

Concept / Approach:

Small-signal linearization uses slopes at the bias point and works only for small variations. For large signals, linear approximations break down; therefore, plotting the DC load line and using the family of I–V curves (graphical method) captures the device behavior across the entire swing, including cutoff and saturation.

Step-by-Step Solution:

Verification / Alternative check:

Practical amplifier design for power stages routinely employs load-line plots and transfer curves to predict clipping, saturation, and distortion—confirming the reasoning.

Why Other Options Are Wrong:

• Any option denying A or R conflicts with standard device physics and design practice.

Common Pitfalls:

• Attempting to use small-signal parameters (r_e, h-parameters) for large excursions; these are valid only near the quiescent point.

Final Answer:

Both A and R are correct and R is correct explanation for A