Crystal diode and transistor amplifier circuit 5

After a large number of holes reach the base region, due to the thinness of the base region, the holes easily cross the base region and run to the edge of the collector junction. A reverse voltage of several volts or even dozens of volts is applied to the collector junction, which can help holes enter the collector region. diodeThat is to say, as soon as the positively charged hole reaches the left side of the collector junction, it is attracted by the negative voltage of the P region on the right side of the collector junction, and then recombines with the electrons sent by the battery in the external circuit to form the collector current Ic.

However, not all holes diffused to the base region can be attracted by the collector electrode, forming a collector current. Because when the hole passes through the base region, it attracts and recombines with the majority carriers electrons in the base region (N-type region), and disappears. diode In addition, a small number of electrons in the base region also run to the emission region to recombine with the hole, forming Ic. Both types of recombination require negative electrons supplied by the external circuit battery, thus forming the base current Ib. However, because the base region is very clear (only one ten thousandth of a meter thick), the time for holes to pass through the base region is only a few hundred millionths of a second, so the number of recombines is very small, and the vast majority of holes reach the collector electrode. Therefore, the collector current Ic is almost equal to the total emitter current Ie.diode