a. If ho e=20 μS at IC=1 mA on Fig. 124, what is the approximate value of ho e at IC=0.2 mA ?

step 1 So for this problem, in part A, the time constant for a circuit is tau -1 times R -C -1. Plutina

A. If ho e=20 μS at IC=1 mA on Fig. 124, what is the...

a. If $h_{o e}=20 \mu \mathrm{S}$ at $I_{C}=1 \mathrm{~mA}$ on Fig. 124, what is the approximate value of $h_{o e}$ at $I_{C}=0.2 \mathrm{~mA} ?$ b. Determine its resistive value at $0.2 \mathrm{~mA}$ and compare to a resistive load of $6.8 \mathrm{k} \Omega$. Is it a good approximation to ignore the effects of $1 / h_{\text {oe }}$ in this case?

a. If $h_{o e}=20 \mu \mathrm{S}$ at $I_{C}=1 \mathrm{~mA}$ on Fig. 124, what is the approximate value of $h_{o e}$ at $I_{C}=0.2 \mathrm{~mA} ?$
b. Determine its resistive value at $0.2 \mathrm{~mA}$ and compare to a resistive load of $6.8 \mathrm{k} \Omega$. Is it a good approximation to ignore the effects of $1 / h_{\text {oe }}$ in this case?

Key Concepts

Dependency on Operating Bias Currents

The value of h_oe depends on the operating point, particularly the collector current (I_C). Since many transistor parameters scale with bias current, understanding how h_oe changes as I_C varies is essential for predicting circuit behavior under different conditions and ensuring accurate biasing in design.

Small?Signal h?Parameters

These parameters represent a linearized model used to analyze the behavior of transistors in small-signal operation. h_oe, one of these parameters, represents the output admittance (or the inverse of the output resistance) of the transistor, and it encapsulates how the transistor’s collector current responds to changes in output voltage, which is critical for accurately designing and analyzing amplifier circuits.

Output Admittance and Resistance

Output admittance, denoted as h_oe, quantifies the sensitivity of the output current to output voltage variations. Its reciprocal gives the output resistance. This resistance plays an important role in determining how the transistor interacts with other load components in the circuit, affecting voltage gain and overall circuit performance.

Approximation in Circuit Analysis

In circuit design, it is common to compare the transistor's output resistance (the reciprocal of h_oe) with external load resistors to determine their influence on circuit performance. When the transistor’s output resistance is much higher than the load resistance, its effect on loading becomes negligible, allowing for simplified analysis. This comparative technique is essential for making justified approximations in complex amplifier networks.

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