Digital switching with BJTs: When a transistor is employed as a logic element, does it primarily toggle between two states called cutoff and saturation?

Introduction / Context:
In digital electronics, transistors function as controlled switches. The central idea is to represent logic 0 and logic 1 by operating a device in two well-separated regions that provide robust noise margins and low static power where possible.

Given Data / Assumptions:

• Device: BJT used as a digital switch.
• Supply rails define logic 0/1 thresholds via resistor networks and device characteristics.
• Design aims for clean transitions and stable states.

Concept / Approach:
The two practical states are cutoff (no base drive, no collector current; output pulled high via load) and saturation (strong base drive forces V_CE low; output near ground). Operating in the linear active region is avoided in steady state because it increases power dissipation and creates ambiguous logic levels. Proper base current sizing ensures the device reaches saturation under worst-case beta and load conditions.

Step-by-Step Solution:

Verification / Alternative check:
Scope measurements show low V_CE(sat) in the ON state and rail pull-up in the OFF state, corresponding to logic levels.

Why Other Options Are Wrong:

Common Pitfalls:
Insufficient base drive (device not saturating), forgetting base-emitter resistors for quick turn-off, and neglecting storage time that slows transitions.

Final Answer:
Correct