transistor 2

Due to the thinness of the base region and the reverse bias of the collector junction, most of the electrons injected into the base region cross the collector junction and enter the collector region, forming a collector current Ic. diode Only a small number (1-10%) of electrons are left to recombine in the holes of the base region. The recombined holes in the base region are replenished by the base power source Eb, thus forming a base current Ibo. According to the principle of current continuity:

Ｉｅ＝Ｉｂ＋Ｉｃ

This means that by adding a small Ib to the base, a larger Ic can be obtained at the collector,diode  which is called current amplification. Ic and Ib maintain a certain proportional relationship, that is:

β１＝Ｉｃ／Ｉｂ

In the formula: β - is referred to as the DC amplification factor,diode

The ratio of the change in collector current △ Ic to the change in base current △ Ib is:

β＝△Ｉｃ／△Ｉｂ

In the formula, β - is referred to as the amplification factor of AC current. Due to the small difference in the values of β 1 and β at low frequencies, sometimes for convenience, the two are not strictly distinguished. diode The value of β is about tens to hundreds.

A transistor is a current amplification device, but in practical use, it often utilizes the current amplification effect of a transistor, which is converted into voltage amplification effect through resistance.diode