Three-terminal voltage regulator, there are two main types, one output voltage is fixed, called fixed output three-terminal voltage regulator, the other output voltage is adjustable, called adjustable output three-terminal stabilizer, the basic principle is the same, all use series type voltage regulator circuit. In the linear integrated voltage regulator, because the three-terminal voltage regulator has only three leading terminals, it has the advantages of few external components, easy to use, stable performance and low price, so it is widely used.
The general products of the three-terminal voltage regulator are 78 series (lower power supply) and 79 series (negative power supply), and the output voltage is represented by the last two numbers in the specific model, there are 5V, 6V, 8V, 9V, 12V, 15V, 18V, 24V and other grades. The output current is distinguished by 78 (or 79) followed by a letter L for 0.1; AM indicates 0.5A, and no letter indicates 1.5A. For example, the value in the 78L05 table is 5V0.1A.