Electronic – NPN Circuit simulation doesn’t agree with book

bjtsaturationspice

I'm trying to understand an exercise reported in Microelectronic Circuit Design by R. C. Jaeger & T. N. Blalock (4th ed, p.237).
$$\beta_F = 50, \beta_R = 1$$.
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I don't agree with the discussion they make.
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Figure 5.19 displays the results of simulation of the collector
current of the transistor in Fig. 5.18 versus the supply voltage V CC
. For V CC > 0, the collector-base junction will be reverse-biased,
and the transistor will be in the forward-active region. In this
region, the circuit behaves essentially as a 1-mA ideal current source
in which the output current is independent of V CC . Note that the
circuit actually behaves as a current source for V CC down to
approximately −0.5 V. By the definitions in Table 5.2, the transistor
enters saturation for V CC < 0, but the transistor does not actually
enter heavy saturation until the base-collector junction begins to
conduct for V BC ≥ +0.5 V

Why does the fact Vcc > 0 automatically implies reverse bias on collector base junction? What if Ic is sufficiently large to produce a voltage drop (on the resistor) bigger than Vcc? In this case the collector base junction will be forward biased, so that the saturation region starts at Vcc clearly different from 0…

In fact, it is essentially what happens if I try to reproduce in SPICE simulation the circuit.. the dark blue line represents Ic which strangely doesn't agree with Fig 5.19!
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Spice schematic:
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I'm a beginner in electronics and SPICE, so I'd like to know where I am wrong.

Best Answer

Actually you are right. The text in the book has an error. There is written Vcc instead of Vce. Vcc must be more than 3,8V to make the Vce > 0 and the transistor to be fully active.

I must admit that I also thought wrongly the working of the circuit in my previous answer version. I did a DC sweep simulation. I placed GND to the emitter to get Vce easily without math, Vce= V(NODE1)

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The voltage of BAT1 goes from 0 to +9V. Vce does not go negative at all. The proper function of the transistor needs Vce > the saturation limit which is about +200mV in this case.