Single-transistor inverter behavior (repaired stem): A common-emitter BJT stage with a collector load resistor and logic-level drive at the base acts as a digital inverter (NOT gate). Is this assessment correct?

Introduction / Context:
Digital logic can be realized with discrete transistors. The simplest example is a single BJT in common-emitter configuration used as a switch to create an inverting transfer characteristic, mapping input high to output low and vice versa.

Given Data / Assumptions:

• Topology: common-emitter with a collector resistor to VCC.
• Base driven by a logic-level signal via a base resistor.
• Transistor operates between cutoff and saturation.

Concept / Approach:
When the base is driven high sufficiently, the BJT saturates and pulls the collector node low (near ground). When the base is driven low (or left unbiased), the transistor is cut off, and the collector resistor pulls the output high toward VCC. This input–output inversion is the hallmark of a NOT gate. TTL families historically implement similar internal structures, although with added complexity for noise margins and fan-out.

Step-by-Step Solution:

Verification / Alternative check:
Plot V_out versus V_in; the transfer shows a high-to-low transition as V_in crosses V_BE(on) with adequate drive to reach saturation.

Why Other Options Are Wrong:

Common Pitfalls:
Under-driving the base (failing to saturate), omitting a base resistor, or overlooking pull-up resistor value and load requirements.

Final Answer:
Correct