In the last line of the second picture, it is not 'In other words, Q3 is a saturated region', but an active region, isn't it? I'm confused because I can't find the errata even if I search for it, so I'm asking. Am I not understanding it well?
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Let me briefly explain how to tell if a TR is blocking, saturated, or active. The cut-off area is easily distinguished as the collector current does not flow. However, saturation and activity can sometimes be confused.
Look at the graph above. The middle part is the active region, and the shaded part on the left is the saturated region.
In the active region, the collector current is changed only by the base current, and there is no change in the collector current by Vce. This is the active area.
On the other hand, in the saturation region, the collector current increases in proportion to Vce. That is, if the collector current is changed by Vce, then that is the saturation region.
In a constant current circuit, even if Vcc changes, the current is always constant. Therefore, the constant current source is unconditionally active.