Question 3.SP.12: Collector characteristics for the Ge transistor of Fig. 3-15......

Schaum’s Outline of Electronic Devices and Circuits [1089587]

Collector characteristics for the Ge transistor of Fig. 3-15 are given in Fig. 3-16. If $V_{EE} = 2 \text{V}, V_{CC} = 12 \text{V}$ , and $R_C = 2 kΩ$ , size $R_E$ so that $V_{CEQ} = -6.4 \text{V}$ .

3.15

3.16

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We construct, on Fig. 3-16, a dc load line having $v_{CB}$ intercept $-V_{CC} = -12 \text{V}$ and $i_C$ intercept $V_{CC}/R_C = 6 \text{mA}$ . The abscissa of the $Q$ point is given by KVL around the transistor terminals:
$V_{CBQ} = V_{CEQ} – V_{BEQ} = -6.4 – (-0.3) = -6.1 \text{V}$

With the $Q$ point defined, we read $I_{EQ} = 3 \text{mA}$ from the graph. Now KVL around the emitter base loop leads to
$R_{E} = \frac{V_{EE} + V_{BEQ}}{I_{EQ}} = \frac{2 + (-0.3)}{3 × 10^{-3}} = 566.7 Ω$

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