How do you understand the three working states of the transistor?

First, from the base bias voltage angle analysis

1, cutoff status: That is, transistor B-pole bias voltage is insufficient, transistor C, e pole no current (or only weak leakage current) through.
2, amplification state: Transistor B pole with the appropriate bias voltage, C, e pole is semi-conduction state, then the current according to the B-pole current and magnification changes in multiples change. For example, the transistor is 30 times times amplification, B-Pole current 10mA is the CE current 300mA, of course, transistor is not linear, depending on the actual circuit structure or transistor characteristics of different.
3, the saturation conduction state, transistor B-pole bias voltage exceeds the amplification requirements, transistor CE current will become larger, and no longer follow the B-pole current changes, is saturated or called conduction state. At this point, the CE can be considered as direct conduction.

Second, from the angle of equivalence of PN Section analysis

When the transistor is saturated, the pressure difference between the c~e is considered to be 0 volts, and you are right to understand that.
Transistor amplification, there must be a pressure difference between the c~e, the common circuit, can be as small as 1V, large people over hundred volts.

Transistors are not difficult to understand, the c~e is equivalent to a variable resistor, the resistance size is controlled by the base current, the larger the base current, the lower the equivalent resistance. When the base current is large, the equivalent resistance is 0,ce equal to the short circuit, which is saturated. The base current is 0 o'clock, the equivalent resistance is infinite, ce equals open circuit, this is the cutoff. When the base current is small, the equivalent resistance is a certain value (the specific size depends on the specific circuit), the base current size changes when the equivalent resistance also changes, which is magnified.

Third, the understanding of the transistor saturation

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Transistor, such as working in saturation is the state of the open, then the double-knot positive bias
It's an explanation in the book.

My own understanding is this:
The saturation and transition from the amplification state, the polar junction and the transmit junction are the results, not the reason.
That is, the transistor first works in the amplification state, the polar electric junction Inverse, the transmission junction is biased
When the base-level current increases, it increases to the non-linear region of the transistor (in this case, the saturation zone), note that in this moment the bias is not changed, that is, the electrode is still the inverse bias, the transmission junction positive bias.
When the transistor fully enters the saturation zone, the polar electrical junction is biased
My core point is that the external reason for the transistor to enter the saturated conduction is that the base-level current increases to the degree of saturation, rather than the transistor conduction by adding 2 forward bias to the transistor

Online Daniel Analysis:

There is no mistake in your understanding, and it is hard to understand this level of effort. But there are a few things that are really important:
1, too concerned about "polar electric Junction". In fact, in the saturated area, that is, the polar electric Junction is positive, also has not reached the pole electrical junction of the positive guide voltage. However, ordinary people will be "biased" misleading.
2, the meaning of saturation: The collector current increases with the base current increases, when the collector current increases to a certain extent, and then increase the base current, the collector current is no longer with the increase, this phenomenon is called saturation. and "transistor as working in saturation, then is double-knot positive deviation" is a phenomenon or causality, also not accounted for. The essence of saturation is that the IC is separated from the linear relationship with IB due to the positive bias of the collector junction (please review the transistor structure).
3, the saturation of the transistor, including the IC tends to 0 of the state, this point please self-experience, understanding.
4, by the transistor launch junction plus a positive guide through the bias, at the same time to set the junction plus positive, transistor must be in the saturation zone (must not be in the amplification area, including the case of the IC zero).
Above these key points, make up a missed lesson also cannot make up. Of course, no one can see the problem.