The difference between diodes and transistors can be understood from their structure and working principle.

The difference between diodes and transistors can be understood from their structure and working principle.

Structural understanding:

A diode is a PN junction, and a transistor is a composite of two PN junctions.

Diodes generally have two PN regions with unidirectional conductivity and are generally used for rectification. And a transistor is an NPN or PNP with three regions, b, e, and c, commonly used as a signal or power amplifier, or electronic switch.

Principle understanding:

1、 Diode working principle

A diode is a two terminal device with unidirectional conductivity, which can be divided into electronic diodes and crystal diodes. Electronic diodes are rarely seen nowadays, and crystal diodes are commonly used. The unidirectional conductivity of a diode is almost universally used in all electronic circuits, and it plays an important role in many circuits. It is one of the earliest semiconductor devices and has a wide range of applications.

2、 The working principle of a transistors

A transistor is a control element mainly used to control the size of the current. For example, in the common emitter connection method (where the signal is input from the base, output from the collector, and the emitter is grounded), when there is a small change in the base voltage UB, the base current IB will also have a small change. Under the control of the base current IB, the collector current IC will have a significant change. The larger the base current IB, the greater the collector current IC, and vice versa, The smaller the base current, the smaller the collector current, that is, the base current controls the change in collector current. But the change in collector current is much greater than the change in base current, which is the amplification effect of the transistor. The ratio of the change in IC to the change in IB is called the amplification factor of the transistor β （ β=Δ IC/ Δ IB, Δ Indicates the amount of change.), Magnification factor of transistor β Usually in the tens to hundreds of times.

transistors  When amplifying a signal, a transistor must first enter a conduction state, that is, establish a suitable static working point, also known as bias, otherwise it will amplify distortion. The secondary transistor mainly has unidirectional conductivity, while the transistor mainly amplifies voltage and current.