Use Figs. 124 through 126. a. If hr e=2 ×10^-4 at IC=1 mA on Fig. 124, determine the approximate

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

Use Figs. 124 through 126. a. If hr e=2 ×10^-4 at IC=1 mA on...

Use Figs. 124 through 126. 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 $A_{v}=210 ?$

Use Figs. 124 through 126.
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

Transistor h-parameters

Transistor h-parameters are a set of small?signal parameters that describe the behavior of a transistor in terms of its current and voltage relationships. They include quantities such as input impedance, forward current gain, reverse voltage gain, and output impedance. Understanding these parameters helps in building and analyzing models of transistor amplifiers for various operating conditions.

Bias Current Dependence

Many small-signal parameters of a transistor, such as the reverse voltage gain parameter h_re, vary with the operating or bias current. Parameter values provided at one current level must be appropriately scaled to other current conditions based on the underlying physics of transistor operation. Recognizing this dependence is crucial for accurate small-signal modeling and for proper design and prediction of amplifier behavior.

Small-Signal Analysis Approximations

In small-signal analysis, certain parameters may be neglected to simplify the analysis if their impact on the overall circuit behavior is minimal. Determining whether a parameter like h_re can be ignored involves comparing its value and associated effects (often through gain-related products) against dominant circuit factors. This approximation process is key in making reliable yet simplified circuit models in engineering practice.

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