Function and working status of transistor products

Product function

The transistor has a current amplification function, which essentially means that the transistor can control the large change in collector current with a small change in base current. This is the most fundamental and important characteristic of a transistor.

We refer to the ratio of Δ Ic/Δ Ib as the current amplification factor of the transistor, denoted by the symbol "β". The current amplification factor is a constant value for a certain transistor, but as the transistor operates, the base

The change in current will also have a certain degree of variation.

working condition

Deadline status

When the voltage applied to the emitter junction of the transistor is less than the conduction voltage of the PN junction, the base current is zero, and the collector current and emitter current are both zero, the transistor loses its current amplification function, and the collector and emitter

The polarity between the poles is equivalent to the open state of the switch, and we call the transistor in the off state.

Magnify state

When the voltage applied to the emitter junction of a transistor is greater than the conduction voltage of the PN junction and is at an appropriate value, the emitter junction of the transistor is forward biased and the collector junction is reverse biased. At this time, the base current is proportional to the collector current

Playing a control role, the transistor has a current amplification effect, with a current amplification factor β=Δ Ic/Δ Ib, at which point the transistor is in an amplification state.

Saturated conduction

When the voltage applied to the emitter junction of the transistor is greater than the conduction voltage of the PN junction, and when the base current increases to a certain extent, the collector current no longer increases with the increase of the base current, but is at a certain value

At this point, the transistor loses its current amplification function, and the voltage between the collector and emitter is very low. The conduction state between the collector and emitter is equivalent to that of a switch. In this state of the transistor, we

It is called saturated conduction state.

Based on the high and low potential of each electrode during the operation of the transistor, the working state of the transistor can be determined. Therefore, electronic maintenance personnel often need to use a multimeter to measure the voltage of each pin of the transistor during the maintenance process,

Thus, the working condition and status of the transistor can be determined.