A transistor has the following values: hfe = 120, hFE = 200, hie = 5 kΩ, hre = 4 × 10-4, and hoe = 2500 μS. What is the value of rʹe for the device?
A) 4 × 10-4 Ω
B) 41.7 Ω
C) 400 Ω
D) 25 Ω

Question

Quizplus · Accepted Answer

The value of $r'_e$ can be calculated using the formula $r'_e = \frac{26mV}{I_E}$, where $I_E$ is the emitter current. However, without knowing $I_E$, we can approximate $r'_e$ using the transconductance ($g_m$) method, where $g_m = \frac{I_C}{V_T}$ and $V_T$ is typically 26mV at room temperature. Given $h_{fe}$ (or $h_{FE}$), we can find $g_m = \frac{h_{fe}}{h_{ie}}$. Since $h_{fe} = 120$ and $h_{ie} = 5k\Omega$, we directly cannot calculate $r'_e$ without the emitter current. However, the correct approach involves understanding the relationship between these parameters and recognizing that $r'_e$ is essentially the inverse of $g_m$ (transconductance), which is not directly calculable with the given values without assuming or calculating $I_E$. The correct choice, based on typical analysis and approximation methods in transistor models, would involve recognizing the role of $h_{fe}$ and $h_{ie}$ in determining the dynamic emitter resistance, but the given values do not directly lead to a straightforward calculation without additional assumptions. Thus, the selection of the correct answer involves understanding typical values and relationships in transistor operation, which might lead to an approximation of $r'_e$ based on standard transistor operation conditions. Given the options and typical analysis methods, the correct answer involves recognizing typical relationships in transistor parameters, but the provided information leads to an approximation rather than a direct calculation.

A Transistor Has the Following Values: Hfe = 120, HFE