Common three-terminal voltage regulator

The function of the voltage regulator is to step down the voltage and stabilize it to a fixed value before outputting it. For example, the three-terminal voltage regulator 7805 can step down a voltage less than 35V to a stable 5V output voltage. It is much better than a circuit that only uses a voltage regulator diode for voltage regulation, and the cost is not very high, so it is still widely used.

Common three-terminal voltage regulators can be divided into two types: positive voltage regulators and negative voltage regulators. The positive voltage ones are 78 series and the negative voltage ones are 19 series. The two series cannot be used interchangeably, so do not confuse them when selecting. The figure shows the appearance of a common 78 series voltage regulator.

Figure 78 series voltage regulator block appearance

Of course, the voltage stabilizer is not limited to the 78 and 79 series, but also includes three-terminal adjustable voltage stabilizer, four-terminal and five-terminal voltage stabilizer, low voltage difference voltage stabilizer, etc. In addition, the voltage stabilizer has small, medium and large power. When replacing, do not use a small power to replace a high power, but there is no problem in using a high power to replace a small power.

Brand is also very important. The error between the voltage value and the nominal value of some poor quality voltage regulators is very large. Some brands of voltage regulators even have very poor thermal stability, which often causes strange failures. Generally speaking, the quality and performance of voltage regulators from brands such as ST (ST), AN (Panasonic), LM (National Semiconductor), and MC (Motorola) are better.