Understanding of three-terminal regulator tube
The function of the three-terminal regulator is to buck the voltage and output it at a fixed value. Security electronic products in the common three-terminal regulator tube has positive voltage output 78 series and negative voltage output 79 series. The three-terminal regulator, as its name implies, has only three pins, namely the input end, the grounding end and the output end.
78/79 series three-end regulator tube composed of the regulator circuit peripheral components, as well as over current, overheating and regulating tube protection circuit, reliable and convenient to use. The number after 78 or 79 represents the output voltage of the three-terminal regulator tube, and there are 8 kinds, respectively 05, 06, 19, 10, 12, 15, 18 and 24. For example, 7805 indicates that the output voltage is positive 5V, and 7909 indicates that the output voltage is negative 9V.
Sometimes 78 or 79 is followed by an L or M, such as 78M12 or 79L24, to distinguish the input current from the package type, etc. The maximum output current of the 78LXX series is 100mA, the maximum output current of the 78MXX series is 0.5A, and the maximum output current of the 78 series is 1.5A. The 78LXX is in to-92 package, and the 78XX and 78MXX are in to-220 or TO202 package. In addition to the negative output voltage and different pin arrangement, the naming method and appearance of 79XX series are the same as 78XX series.
Note: the input, output and grounding of the three-terminal voltage regulator should not be misconnected. Generally, the minimum output and output voltage difference of the three-end voltage regulator are 2V, otherwise stable voltage cannot be output. It is best to keep the voltage difference at 4 ~ 5V. In actual application, voltage difference is bigger, current is bigger, the radiator that installs on 3 end stable voltage tube also should be bigger, otherwise stable voltage performance will become poor, damage even.