What Is the Collector Current?

The current amplification factor of the transistor is also called the current distribution coefficient of the transistor, and the letter is the Greek letter . Among the three currents of the transistor, one current changes, and the other two currents also change proportionally. For example, the change amount of the base current Ib I b = 10 A and = 50. According to the relational expression of I c = I b, the change amount of the collector current I c = 50 × 10 = 500 A, and the base current pair is realized. The control and amplification of the collector current embodies the principle of "controlling the large with the small and making the strong with the weak".

in

The DC current amplification factor is the multiple that the emitter current is greater than the base current is called the DC current amplification factor of the transistor.

Adding a small IB to the base can get a larger IC on the collector. This is the so-called current amplification effect. The IC and IB maintain a certain proportional relationship, that is:

= IC / IB

In the formula: -called the DC amplification factor

The ratio of the change amount of the collector current IC to the change amount of the base current IB is:

= IC / IB

in the formula is called the AC current amplification factor. Because the values of 1 and are not much different at low frequencies, for convenience, the two are not strictly distinguished.

The base current IB and the collector current IC are also called input current and output current, respectively. The output current is considerably increased compared to the input current. This phenomenon is called amplification.

Here, the ratio of IC to IB is called the DC current amplification factor hFE, as shown in the following formula:

The value of the DC current amplification factor of the transistor is usually in the range of about 50 to 1,000.

Working in a dynamic transistor, the real signal is an AC signal superimposed on DC. The change of the base current is IB, and the corresponding change of the collector current is IC, then the AC current amplification factor is:

= Ic / Ib

Where is called the AC current amplification factor. Because the values of 1 and are not much different at low frequencies, sometimes for the sake of convenience, the two are not strictly distinguished. The value of is about several tens to more than one hundred ^[1] .