The bipolar active load diff-amp in Figure 14.18 is biased at (V^{+}=5 mathrm{~V}) and (V^{-}=-5 mathrm{~V}). The

Question:

The bipolar active load diff-amp in Figure 14.18 is biased at $V^{+}=5 \mathrm{~V}$ and $V^{-}=-5 \mathrm{~V}$. The transistor parameters are $V_{A N}=120 \mathrm{~V}, V_{A P}=80 \mathrm{~V}$, $v_{B E}(\mathrm{npn})=v_{E B}(\mathrm{pnp})=0.6 \mathrm{~V}, I_{S 1}=I_{S 2}$, and $I_{S 3}=5 \times 10^{-15} \mathrm{~A}$. Let $v_{1}=v_{2}$. Determine the value of $I_{S 4}$ for which $Q_{4}$ has a C-E voltage of

(a) $v_{E C 4}=0.6 \mathrm{~V}$,

(b) $v_{E C 4}=1.2 \mathrm{~V}$, and

(c) $v_{E C 4}=2.5 \mathrm{~V}$.

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