The difference between MOS tube and bipolar transistor

The difference between MOS diode and bipolar transistor

MOS diode and bipolar transistor (BJT) are two common transistordevices. They have obvious differences in working principle, structure and performance. This article will compare and analyze them. If you are interested in the content that will be involved, please continue to read the following, hoping to help you.

structure:

BJT has three regions: Emitter, Base and Collector. The emitter region and the collector region are N-type or P-type semiconductors, and the base region is another semiconductor material doped from one side to the other, forming a PNP or NPN structure.

 MOS transistor are divided into N-channel type and P-channel type, and their basic structure is based on a four-layer composite structure: substrate (Substrate), insulating layer (Insulator), gate (Gate) and source/drain (Source) /Drain). The substrate is a high-purity semiconductor wafer, the insulating layer is usually silicon dioxide or silicon nitride and other materials, the gate is a layer of metal or polycrystalline silicon and other materials with good conductivity covering the insulating layer, and the source/drain is The region formed by P or N type semiconductor is connected to the substrate.

working principle:

The working principle of BJT is that a small number of carriers in the base region are amplified by injection, that is, the size of the current flow is controlled. When the positive voltage of the base region is applied to a certain extent, the carriers in the base region are injected into the collector region, and the generated current is amplified.

The working principle of the  MOS diode  is to form an electric field between the gate and the drain, which can control the number of electrons in the source/drain, thereby controlling the flow of current. In the channel of the MOS diode , there is a thin oxide insulating layer (also called gate oxide layer). When a certain voltage is applied to the gate, the semiconductor under the insulating layer will generate a reverse bias. This causes a band bend in the semiconductor, which creates a conduction channel between the source and drain, controlling the flow of current.

Performance comparison:

BJT and  MOS diode  each have different performance characteristics. The BJT control circuit is simple and robust, suitable for amplifying large signals and high-precision amplification, and has a larger linear gain range. But its main disadvantages are low input impedance, high noise, and output voltage saturation.

 MOS diode  are suitable for controlling large and small signals, controlling large current and high frequency signals. It has high input impedance, low noise, and low power consumption, and can be made into high-power devices and high-frequency devices, but its main disadvantage is the existence of gate capacitance, which may cause problems such as distortion and interference, and requires an external static voltage control.

That's the end of this article. Guangdong Youfeng Microelectronics Co., Ltd. will continue to work hard to provide users with more and better technical information and product information. In general, both devices have their own advantages and disadvantages, and must be selected according to specific application scenarios. For example, in fields such as power amplification, BJT is more commonly used, and in integrated circuit devices, especially in high-speed and high-frequency fields,  MOS diode  are more widely used.