MC7809ECTBU

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In recent years, the variety and complexity of semiconductor devices have been greatly improved, and the power management IC (PMIC) has become more and more popular. Linear voltage regulators are one of the important categories in PMIC. MC7809ECTBU is one of the typical linear regulators. It is widely used in many electronic systems with its excellent performance. This paper will discuss the application field and working principle of MC7809ECTBU in detail.

Application Field

MC7809ECTBU is a three-terminal adjustable linear regulator. It is available in TO-220 packages, and the output voltage is adjustable with an external feedback resistor and provides very good electrical characteristics. Its typical output current is up to 1.5A, the dropout voltage is 2.25V, and the input voltage range is 2.5V-25V. Thus, MC7809ECTBU is suitable for DC/DC buck converters and many other applications. Specifically, it can be applied in the following system:

• Automotive and Motor Control Systems;
• Information and Telecommunications Systems;
• Consumer Electronics;
• Industrial Automation;
• Instrumentation and Measurement.

Working Principle

MC7809ECTBU is a special voltage regulator composed of transistors, resistors, diodes and other components. As shown in the figure below, its circuit diagram mainly includes two parts: voltage reference, error amplifier and output stage. The voltage reference provides a stable reference voltage, and the error amplifier compares the reference voltage and input voltage of the regulator. If the input voltage is lower than the reference voltage, the error amplifier will output a positive voltage. Then, it will be amplified by the output stage, and finally, it output a voltage to drop the input voltage. MC7809ECTBU can also provide overload protection, overvoltage protection, short circuit protection and current limit protection.

The following is a detailed explanation of the working principle of the MC7809ECTBU. When the voltage drops, the transistor in the voltage reference part will start to work and turn on, and the current flows through the resistor to increase the voltage and finally forms a stable reference voltage. At the same time, the input voltage is also applied to the negative input end of the error amplifier, and the reference voltage is applied to the positive input end. If the input voltage is lower than the reference voltage, the output voltage of the error amplifier will be positive, and the transistor in the output stage will be turned on. Then, the current from the negative power supply enters the output stage, and since the output stage is in the forward conduction state, the output voltage of the output stage drops, and thus drops the system voltage.

Conclusion

In conclusion, MC7809ECTBU is a three-terminal adjustable linear regulator available in TO-220 packages. It has a wide input voltage range and a maximum output current of 1.5A. Its excellent electrical characteristics make it suitable for DC/DC buck converters and many other applications. The working principle of MC7809ECTBU consists of two parts: voltage reference and error amplifier, which allows it to provide overload protection, overvoltage protection, short circuit protection and current limit protection.

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