嵌入式 - 什么是双极晶体管

What is a bipolar transistor?

双极晶体管是一种由 pn 结组成的晶体管，也称为双极结晶体管（BJT）。场效应晶体管是一种单极器件，而双极晶体管之所以叫双极晶体管，是因为它的工作涉及两种电荷载流子--空穴和电子。

Bipolar transistors are a type of transistor composed of pn junctions, which are also called bipolar junction transistors (BJTs). Whereas a field-effect transistor is a unipolar device, a bipolar transistor is so named because its operation involves two kinds of charge carriers, holes and electrons.

由于双极晶体管是最早发明的晶体管，所以当人们简单地说到 "晶体管 "时，有时指的就是双极晶体管。

Since the bipolar transistor was the first transistor to be invented, when one simply says "transistors," it sometimes means bipolar transistors.

根据结的类型，双极晶体管分为 npn 和 pnp 两种类型。双极晶体管的结构看起来是对称的。

Two types of bipolar transistor are available, known as npn and pnp, based on the type of junction. The structure of a bipolar transistor looks symmetrical. 

NPN Transistor:  NPN 晶体管

大多数电荷载流子是电子。电流从集电极流向发射极。发射器向基极发射电子，这些电子被吸引到集电极。

偏压： 基极需要比发射极更正，晶体管才能导通。通常用于共发射极配置，即发射极接地。

由于电子（NPN 中的多数载流子）与空穴（PNP 中的多数载流子）相比具有更高的迁移率，因此通常速度更快，可处理更大的电流。

更常用于电路中，因为它们的开关和放大效率通常更高。广泛应用于数字电路、开关、放大器和其他通用应用。

NPN 晶体管因其更快的开关速度和更大的电流能力而得到更广泛的应用。它们是大多数数字和开关应用的首选。

The majority charge carriers are electrons. Current flows from the collector to the emitter. The emitter emits electrons into the base, and these electrons are attracted to the collector.

Biasing: The base needs to be more positive than the emitter for the transistor to turn on. Typically used in common-emitter configuration where the emitter is connected to ground.

Generally faster and can handle higher current because electrons (majority carriers in NPN) have