Question

At high frequencies, a transistor model must include

• A. Junction capacitances
• B. Only current sources
• C. Only resistances
• D. Ideal voltage sources

Hint:

High-frequency transistor analysis requires inclusion of \[ \boxed{\text{Internal junction capacitances}} \] to account for frequency-dependent behavior.

Answer 1

The Correct Option is A

Step 1: Recall the transistor model at high frequencies. At high frequencies, the effects of the internal junction capacitances become significant. These include: \[ \begin{aligned} & C_{be} \quad \text{(Base-Emitter capacitance)}, & C_{bc} \quad \text{(Base-Collector capacitance)}. \end{aligned} \]

Step 2: Choose the correct option. Therefore, the high-frequency transistor model must include \[ \boxed{\text{Junction capacitances}.} \] Hence, \[ \boxed{(A)} \] is the correct answer.