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

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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