RB=8kQ VIN igure 2(a) 10VQ R=2ΚΩ VOUT B Figure 2(b) R₁=23kQ R=2kQ C₁ 10V VIN R₂=3kQ RE=2000 C₂ Figure 3(a) VBE -O VOUT
Figures 2(a) and 2(b) show a simple transistor amplifier
and a simplified large signal model of a transistor,
respectively.
(i) Assuming the transistor is in the active region,
redraw the circuit in Figure 1(a) by using the
simplified large signal model (Figure 1b) in place
of the transistor, and derive an expression
relating VOUT to VIN.
[4 marks]
(ii) Based on the expression in a(i), sketch the
voltage transfer characteristics curve, i.e., VOUT
vs VIN. Comment on the limitations of the
simplified large signal model.
[3 marks]
(iii) Assuming VBE(on) = 0.7V and VCE(saturation) = 0.2V,
redraw your sketch to include its cut-off, active
and saturation regions. Mark on this sketch a
suitable quiescent operating point for the circuit
and explain your reasoning.
[3 marks]
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