The base-emitter voltage of an ideal transistor is

Question

Examoogle · Accepted Answer

0

Explanation: In the study of ideal electronic devices, an ideal transistor model assumes zero voltage drop across the forward-biased base-emitter junction ($V_{BE} = 0	ext{ V}$). This abstraction is used in circuit analysis to simplify calculations by treating the junction as a perfect switch with no threshold voltage or internal resistance.

Working Principle: In a real BJT, the base-emitter junction acts as a p-n diode which requires a threshold voltage (typically $0.7	ext{ V}$ for Silicon) to overcome the built-in potential barrier. In the ideal model, this potential barrier is assumed to be zero, meaning the junction conducts current the moment any positive forward bias is applied.

Key Formulas: $V_{BE} = 0	ext{ V}$ — ideal base-emitter voltage requirement; $I_B > 0$ — condition for ideal conduction

Key Points: Ideal components are theoretical abstractions used for simplified circuit analysis.; Real transistors exhibit a voltage drop due to the depletion layer width and carrier recombination.; The $0.7	ext{ V}$ value is the standard practical approximation for Silicon BJTs.; The $0.3	ext{ V}$ value is the standard practical approximation for Germanium BJTs.

Advantages: Simplifies complex network analysis; Allows for quick manual estimation of circuit states

Disadvantages: Lacks precision compared to practical device models; Does not account for power dissipation caused by junction drops

Applications: Ideal switch analysis in digital logic; Simplified large-signal modeling

Additional Info: Option B ($0.3	ext{ V}$) is the threshold for Germanium transistors.. Option C ($0.7	ext{ V}$) is the threshold for Silicon transistors.. Option D ($1	ext{ V}$) is significantly higher than typical semiconductor junction thresholds.

Answer: A is correct — The ideal transistor model assumes no voltage drop across the base-emitter junction, defined as $V_{BE} = 0	ext{ V}$.

Exam Tip: Always verify if the question asks for an 'ideal' or 'practical' transistor, as this choice fundamentally changes your calculation of load lines and biasing points.

Related Questions

Discussion (0)