The 7805 voltage regulator is a series-regulated voltage regulator. It is equipped with overheating, overcurrent, and overvoltage protection circuits inside. Then the voltage regulator has only three pins: the input, output, and GND terminal. The 7805 connects the rectified and filtered unstable DC voltage to the input terminal of the voltage regulators. After passing through the voltage regulators, we can obtain a stable DC voltage at the output. Although we get a fixed voltage at the output terminal, we can use external components to vary the voltage and current to achieve our goal.
Classification of Regulators
Whether to adjust the output voltage
The output voltage of the voltage regulator is fixed and adjustable. The manufacturer pre-adjusted the fixed output voltage, and the output voltage is a fixed value. For example, the output voltage in the L7805 voltage regulator is +5V.
The output voltage of the adjustable voltage regulators can be adjusted in a wide range with a few external components. When changing the value of external components, we can obtain the required output voltage. For example, the output voltage in the LM317 voltage regulators can be continuously adjustable in the 1.2 ~ 37V.
The positive and negative values of the output voltage
The voltage regulator that outputs a positive voltage (78××) is divided into seven grades from 5 to 24V. For example, 7805, 7806, 7809, etc., where 78 indicates that the output voltage is a positive value, and the following number 05 indicates the regulated value of the output voltage. The output current is 1.0A (requires a radiator).
The voltage regulator that outputs a negative voltage (79××) is divided into seven grades of -5～-24V. For example, 7905, 7906, 7912, etc., where 79 means that the output voltage is a negative value, and the number 05 behind it means the regulated value of the output voltage. The output current is 1.0A (requires a radiator).
The difference in output current
The output current of the voltage regulator is divided into large, medium, and small, and different symbols represent them.
The output is a small current code-named “L.” For example, 78L××, the maximum output current is 0.1A.
The output is a medium current, code-named “M.” For example, 78M××, the maximum output current is 0.5A.
The output is a high current with no code. For example, 78××, the maximum output current is 1.5A.
Note: Each manufacturer has different markings and models for different output currents. Please refer to the product datasheet when purchasing.
Outline Drawing and Parameters of Voltage Regulator
The package of the voltage regulator: in-line package TO-220 and SMD package TO-252. See Figure 1 and Figure 2 for familiar outline drawings. For the main parameters of the regulator, please refer to the product specification.
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| Figure 1: TO-220 | Figure 2: TO-252 |
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