a. If hr e=2 ×10^-4 at IC=1 mA on Fig. 124, determine the approximate value of hr e at 0.1 mA .

step 1 So you have a function f of x is equal to ln of x and you want to estimate what the slope is at

A. If hr e=2 ×10^-4 at IC=1 mA on Fig. 124, determine the...

a. If $h_{r e}=2 \times 10^{-4}$ at $I_{C}=1 \mathrm{~mA}$ on Fig. 124, determine the approximate value of $h_{r e}$ at $0.1$ $\mathrm{mA} .$
b. For the value of $h_{r e}$ determined in part (a), can $h_{r e}$ be ignored as a good approximation if $A_{v}=210 ?$

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Key Concepts

Small-signal Transistor Modeling

This concept involves analyzing transistors by linearizing their behavior around a bias point, allowing the use of equivalent circuits with parameters that capture the essential devices' small changes. Such models simplify the understanding of amplification and frequency response in analog circuits.

Hybrid (h) Parameters

h-parameters are a set of linear coefficients used to describe the small-signal behavior of transistors. They include parameters like h_ie, h_fe, h_oe, and h_re, with h_re representing the reverse voltage transfer from output to input. These parameters are useful for designing and analyzing amplifier circuits.

Dependence of Transistor Parameters on Bias Current

Transistor parameters, including h_re, typically change with operating conditions such as bias current. Recognizing how these parameters scale with current is important for predicting the performance of a transistor in different regions of operation.

Simplifying Circuit Analysis by Neglecting Minor Parameters

In amplifier design, if a parameter is significantly smaller than other dominant effects (for example, when its contribution is negligible compared to a high voltage gain), it can be approximated as zero. This allows engineers to simplify circuit models without compromising accuracy in many practical applications.

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