What is Voltage Regulator 7805 – Internal Block Diagram and Applications

In this article, we will discuss the definition, internal block diagram, circuit configuration, and applications of voltage regulator 7805 IC. Let’s begin with the basic introduction of voltage regulator.

A voltage regulator is an essential element of power supplies used in several electrical and electronic devices such as computers, amplifier, automobile alternator, mobile chargers, etc. A voltage regulator is basically an electronic circuit that generates a regulated voltage of fixed value from an unregulated fluctuating voltage.

A voltage regulator is required in a circuit because all voltage sources cannot provide a steady voltage due to change in the load current and other circuit parameters like temperature. Therefore, the primary function of a voltage regulator is to convert the fluctuating voltage of a voltage source into a constant and steady output voltage.

Today, we use voltage regulators in the form of integrated circuits (ICs). In this article, we will discuss one of such voltage regulator ICs named voltage regulator 7805.

What is Voltage Regulator 7805?

The voltage regulator IC 7805 is a member of the 78xx series of voltage regulator ICs. The voltage regulator 7805 is a linear voltage regulator. In the 78xx series of voltage regulators, the “xx” represents the steady output voltage produced by the voltage regulator. Therefore, for the voltage regulator IC 7805, the steady output voltage is +5 V DC.

It is to be noted that the maximum input voltage of the voltage regulator IC 7805 is 35 V. Therefore, the voltage regulator 7805 can produce a steady output voltage of 5 V for any value of input voltage less than or equal to 35 V. Hence, the 34 V is the threshold limit of the input voltage for a voltage regulator 7805 IC.

PIN Diagram of Voltage Regulator 7805 IC

The PIN diagram of the voltage regulator IC 7805 is shown in Figure-1.

PIN-1 (Input PIN)

The PIN-1 is used to provide input voltage to the voltage regulator 7805. The value of voltage connected at the PIN-1 should be in the range of 7 V to 35 V. Hence, the unregulated voltage is connected to PIN-1 of the voltage regulator 7805 IC. It is important to note that if we provide 7.2 V at the PIN-1, then the PIN-1 achieves its maximum efficiency.

PIN-2 (Ground PIN)

The PIN-2 of the voltage regulator 7805 IC is connected to the ground. Therefore, for both input and output circuit, the PIN-2 remains at the 0 V potential.

PIN-3 (Output PIN)

For voltage regulator 7805 IC, the PIN-3 is used to take the fixed regulated output voltage of 5 V. But, practically, the output voltage of voltage regulator 7805 ranges from 4.8 V to 5.2 V.

Internal Block Diagram of Voltage Regulator 7805 IC

The internal block diagram of the voltage regulator 7805 IC is shown in Figure-2.

From the internal block diagram, it is clear that the voltage regulator 7805 IC consists of a starting circuit, a current generator, reference voltage, SOA protection circuit, error amplifier, thermal protection circuit, and series pass element.

Here, the error amplifier is an operational amplifier. A zener diode is provided in the circuit of the voltage regulator 7805 IC for providing the reference voltage. The series pass element is a transistor which dissipates additional energy in the form of heat. A heat sink is provided for thermal protection to dissipate the heat produced due to high supply voltage. SOA stands for Safe Operating Area and it is the condition of current and voltage in which the device is expected to work without any damage. The SOA protection is implemented by using a BJT with a series resistor and an auxiliary transistor.

Heat Dissipation in Voltage Regulator 7805 IC

In voltage regulator 7805 IC, a large amount of energy is exhausted in the form of heat. This is because there is a high difference between the input and output voltage which is converted in heat within the regulator IC. Therefore, to dissipate this heat, a heat sink is provided with the voltage regulator IC 7805. If we do not use the heat sink, the excessive heating of the regulator IC may cause malfunctioning of the device.

Features of Voltage Regulator 7805 IC

The following points highlights the important features of the voltage regulator 7805 IC −

• Voltage regulator 7805 uses less number of component to work properly.
• Its minimum and maximum input voltage are 7 V and 35 V respectively.
• Voltage regulator 7805 can deliver an output current of upto 1.5 A.
• The operating current of the voltage regulator 7805 IC is 5 mA.
• Voltage regulator 7805 provides all the necessary protections such as protection against the short circuit and thermal overload.

Advantages of Voltage Regulator 7805 IC

The chief advantages of the voltage regulator 7805 IC are listed below −

• It does not require any extra component to handle its output voltage.
• It has built-in protection against short circuit and overvoltage.
• In voltage regulator 7805 IC, a heat sink can be provided through the ground terminal to protect it from heat produced due to high currents or short circuit currents.

Applications of Voltage Regulator 7805 IC

In electrical and electronic circuits, the voltage regulator 7805 IC has a wide range of applications. Voltage regulator 7805 IC is used in mobile changers, UPS power supplies, portable CD players, current regulators and fixed output regulators, and adjustable output voltage regulators. It is also used as a +5V voltage regulator.

Conclusion

Voltage regulator 7805 IC is one of the most widely used voltage regulator IC in different electrical and electronic circuits. It takes an unregulated voltage of 7 V to 35 V and produces a fixed regulated output voltage of 5 V DC.

The voltage regulator 7805 is a member of 78xx series, where the "78" represents a positive voltage regulator and "xx" represents the regulated output voltage. Hence, the IC 7805 is a positive voltage regulator having +5 volts regulated output voltage.