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The BJTs in the Darlington follower of Fig. P8.98 have = 100. If the follower is fed
Chapter 8, Problem 8.98(choose chapter or problem)
The BJTs in the Darlington follower of Fig. P8.98 have \(\beta=100\). If the follower is fed with a source having a \(100-\mathrm{k} \Omega\) resistance and is loaded with \(1 \mathrm{k} \Omega\), find the input resistance and the output resistance (excluding the load). Also find the overall voltage gain, both open-circuited and with load. Neglect the Early effect.
Questions & Answers
QUESTION:
The BJTs in the Darlington follower of Fig. P8.98 have \(\beta=100\). If the follower is fed with a source having a \(100-\mathrm{k} \Omega\) resistance and is loaded with \(1 \mathrm{k} \Omega\), find the input resistance and the output resistance (excluding the load). Also find the overall voltage gain, both open-circuited and with load. Neglect the Early effect.
Step 1 of 8
The emitter current for transistor 2 is 10 mA.
Calculate the emitter resistance for the second transistor.
\(\begin{aligned}
r_{E 2} & =\frac{V_{T}}{I_{E 2}} \\
& =\frac{25 \mathrm{mV}}{10 \mathrm{~mA}} \\
& =2.5 \Omega
\end{aligned}\)
Consider the below conditions:
\(\begin{array}{l}
I_{C 2}=I_{E 2} \\
I_{B 2}=\frac{I_{E 2}}{\beta}
\end{array}\)