In the electronic component industry, crystal triode and field effect transistor are two kinds of highly respected electronic components. Especially in switching power supply, they are favored by electronic engineers. But how to choose crystal triode and field effect transistor, crystal triode for short, and field effect for the newly introduced purchasing? Like transistors, transistors, which have the characteristics of amplification and switching, are one of the core devices in electronic devices and are widely used. Triode and field effect transistor have the same characteristics and shape, but their working principles are different. Common triode is a current control device, and two-field effect transistor is a voltage control device.
Description of Crystal Triode and Field Effect Transistor
what is crystal triode?
A control device for voltage amplification or circuit amplification. The voltage Vbc between the base and collector can be amplified to tens or hundreds of times, and output in the form of Vce between the emitter and collector. The base current LB can be amplified by beta times, and then output in the form of IC at the collector.
what is field effect transistor(FET)
The original is much smaller than the transistor. The transistor is a small silicon wafer, but the structure of the field effect transistor is more complex than the transistor. The channel of the field effect transistor is usually several nanometers. That is to say, the fabrication of the “silicon wafer” of the field effect transistor is more complex and much smaller than the transistor. But again, industrial system. The integrated circuit of the field effect transistor is much simpler than that of the transistor, and the integrated density is much higher than that of the transistor. The field effect transistor is a voltage-controlled current transistor and a current-controlled current transistor. Generally, it can not be directly replaced unless the circuit structure is changed slightly.
Selection Skills of Crystal Triode and Field Effect Transistor
Selection Techniques of Crystal Triode
It is necessary to understand the types and materials of transistors. NPN and NPP are commonly used. These two kinds of transistors require different polarity of voltage when they work, so they can not be replaced each other. There are germanium material and silicon material in the transistor. The biggest difference between them before is that the voltage is not the same. In the amplifier circuit, if the same type of germanium tube is used to replace the same type of silicon tube, and vice versa, it is generally possible, but the necessary adjustment should be made on the base bias voltage. Because their starting voltage is not the same, but whether the transistors of different materials can be interchanged in the pulse circuit and the switching circuit must be analyzed in detail, and it must not be replaced blindly.
Selection Techniques of Field Effect Transistor
Selecting a field effect transistor requires only three steps:
- Choose the appropriate route (N or P channel)
- To determine the rated current of field effect transistor, after selecting the rated current, it is necessary to calculate the conduction loss.
- To determine the heat requirement, the designer must take into account the worst and the real situation in the design. It is generally recommended that the worst-case results be used, because the results provide a greater margin of safety to ensure that the system does not fail.