In addition, there is generally a single chip microcomputer for digital control, and the related contents will involve the minimum system of single chip microcomputer, AD/DA conversion, digital tube /LCD display, keyboard input and so on.
The most difficult part of power supply lies in the design of power supply circuit, the acquisition of indicators, such as output voltage, current and necessary accuracy indicators, as well as some characteristic parameters of power supply, such as load capacity, ripple coefficient and so on. Generally speaking, the problem of power supply is not easy to do. There are many contents of analog electricity.
Among your four categories, the simplest is the control category, with the most people doing it every year, followed by the data acquisition category. The power supply is similar to the instrument category, and there may be more instruments (the instrument category mainly involves the basic content of analog electricity, which is less difficult than the power supply), and the communication category is the least, mainly because the high frequency is too difficult and there are many variables, and the state may change at a beat.