7805 Voltage Regulator IC Pinout, Circuit, Datasheet, and Uses

In the realm of electronic devices, a regulated power supply holds paramount importance. This is particularly crucial due to the utilization of semiconductor materials in these devices, which operate within specific voltage and current parameters. Any deviation from these predefined values may result in damage to the device. While batteries serve as primary DC supply sources, prolonged usage in sensitive electronic circuits becomes impractical as they experience a gradual decline in potential and eventual depletion.

Batteries offer varying voltage ranges, such as 1.2 Volts, 3.7 Volts, 9 Volts, and 12 Volts. Since a significant proportion of integrated circuits operate optimally with a 5V supply, a reliable 5V supply, often facilitated by a voltage regulator, becomes imperative. The 7805 voltage regulator, which is a notable example of the 78XX series of linear voltage regulators, efficiently delivers a regulated 5V output. This article will explore one of the most commonly used regulator ICs: the 7805 Voltage Regulator IC. It will cover its pinout, circuit, working, uses, datasheet, and more details.

What is 7805 Voltage Regulator IC?

The 7805 is a three-terminal linear voltage regulator integrated circuit, furnishing a consistent +5V output voltage within a variable input voltage range. The 7805 IC is a revered choice in numerous projects due to its versatility. The terminology "7805" holds significance: the "78" denotes its role as a positive voltage regulator, while the "05" indicates its provision of a 5V output. Consequently, the 7805 reliably delivers a +5V output voltage.

This IC has a maximum output current capacity of 1.5A. However, it is susceptible to significant heat dissipation, necessitating a heat sink, particularly in projects with higher current consumption. For instance, if the input voltage is 12V and the consumption is 1A, the heat dissipated can be calculated as (12-5) * 1 = 7W, highlighting the importance of managing this 7 Watts heat.

LM7805 Voltage Regulator IC

LM7805 Pinout

As previously noted, the 7805 is a three-terminal device featuring the following pins: 1. INPUT, 2. GROUND, and 3. OUTPUT. The illustration below visually represents these pins on a standard 7805 IC in a TO-220 package.

The pin configuration and description for the 7805 are elucidated in the table presented next:

Pin Configuration

Pin No.	Pin Name	Description
1	Input (V+)	Unregulated Input Voltage
2	Ground (Gnd)	Connected to Ground
3	Output (Vo)	Outputs Regulated +5V

7805 Voltage Regulator Feature & Specifications

• Positive Voltage Regulator for 5V

• Accepts Input Voltages from 7V to 25V

• Operational current (IQ): 5mA

• Current rating (Ic): 1A

• Capable of delivering currents up to 1.5A

• Output Voltage Range: 4.8V to 5.2V

• Efficient operation with minimal component requirements

• Equipped with thermal shutdown and internal current limiting features

• Incorporates internal Thermal Overload and Short Circuit current limiting protection

• Maximum Junction Temperature: 125 degrees Celsius

• Available in TO-220 and KTE package variants

7805 Voltage Regulator IC Circuit

7805 IC Schematic

At the core of the 7805 IC lies a transistor (Q16) responsible for regulating the current between the input and output, thereby controlling the output voltage. Ensuring voltage stability is the bandgap reference (depicted in yellow).

Taking the scaled output voltage as input (utilizing Q1 and Q6), the circuit generates an error signal (directed to Q7) to indicate whether the voltage deviates from the desired range.

A critical function of the bandgap is to furnish a consistent and precise reference, maintaining stability despite fluctuations in the chip's temperature.

The error signal from the bandgap reference undergoes amplification through the error amplifier (colored orange). This amplified signal governs the output transistor via Q15, forming a negative feedback loop that regulates the output voltage.

The startup circuit (colored green) ensures an initial current supply to the bandgap circuit, preventing it from getting stuck in an "off" state. The purple circuit protects overheating (Q13), excessive input voltage (Q19), and surpassing output current (Q14).

These protective circuits either reduce the output current or deactivate the regulator, safeguarding it from potential damage in the event of a fault. The voltage divider (depicted in blue) scales down the voltage on the output pin for utilization by the bandgap reference.

Scaling the Output

The scaled output 7805 serves as the input voltage (Vin) for the bandgap reference, with the bandgap producing an error signal as the ultimate output. In the 7805, the bandgap circuit diverges from the conventional approach by eliminating the internal feedback loop in traditional bandgap references. Instead, the entire chip functions as the feedback loop.

When the output voltage is at the desired 5V level, the voltage divider yields 3.75V at Vin. Any alterations in the output voltage initiate changes in Q6 and R7, influencing the voltage at the base of Q7.

This variance is then magnified by Q7 and Q8, generating the error output. Consequently, the error output either reduces or increases the current flowing through the output transistor. The negative feedback loop ensures adjustments to the output voltage until it aligns with the correct value.

7805 as +5V Voltage Regulator

Displayed below is a standard implementation diagram for the 7805 IC. Only two capacitors, with values of 33uF and 0.1uF, are required to activate this IC.

The 0.33uF input capacitor is crafted from a ceramic material to address input inductance concerns, while the 0.1uF output capacitor, also ceramic, contributes to circuit stability. Placing these capacitors close to the terminals ensures optimal functionality. It is essential to opt for ceramic-type capacitors due to their superior speed compared to electrolytic capacitors.

LM7805 Circuit–7805 as adjustable output Regulator

The IC can function as a variable output voltage regulator, providing the flexibility to tailor the output voltage to a desired level through the circuit outlined below.

In this configuration, the input voltage has a permissible range of 9V to 25V, and the output voltage is variable based on the resistance values of R1 and R2. The specific value can be computed using the formula provided:

Where, Vxx=5, IQ = 5*10-3

LM7805 Circuit–How does the 7805 IC work in a circuit?

The circuit consists of:

• A transformer

• Capacitors

• Voltage regulator (7805)

• Diodes (Bridge rectifier)

• Fuse

The 230V AC power is directed to the transformer, where it undergoes conversion into oscillating DC power through the bridge rectifier. To regulate the current from the transformer, a fuse is in place, limiting it to 1A.

Capacitors positioned at both ends of the circuit serve as ripple filters for incoming current. The 12V DC unregulated output from C1 is directed to the voltage regulator, emerging as a stable 5V. The D1 diode is protective, preventing damage from reverse bias-induced current spikes.

Maintaining a minimum 2.5V difference between input and output voltages is crucial. Heat dissipation, a consequence of power loss, necessitates using a heat sink for the 78058 IC.

Opting for an AC power source proves more convenient than a DC counterpart. The inherent instability of DC batteries, prone to frequent discharge, diminishes voltage output over time.

LM7805 Circuit–Applications of the 7805 Linear Voltage Regulator

In addition to functioning as a +5V regulator and an adaptable voltage regulator, the LM7805 is suitable for circuits necessitating:

1. Safeguarding against reverse bias

2. Maintaining a regulated dual power supply

3. Providing a consistent +5V output for applications such as microcontrollers, sensors, and various projects.

Practical implementations encompass:

1. Charging DC batteries

2. Powering phone chargers

3. Supporting portable CD players

4. Enabling uninterrupted power supplies (UPS)

How 7805 Voltage Regulator IC Working

The provided configuration facilitates the conversion of AC power supply to DC. This circuit incorporates a transformer, a bridge rectifier, the IC 7805 linear voltage regulator, and capacitors.

The circuit is bifurcated into two segments. AC mains transform DC in the initial segment, while the subsequent segment refines this DC into a regulated 5V DC. Initially, a step-down transformer lowers the voltage from 230V to 12V by connecting its primary winding to the main supply—the secondary winding links to the bridge rectifier.

A 1A fuse is strategically placed between the bridge rectifier and the transformer to interrupt the current flow within the 1A circuit. The bridge rectifier produces rectified DC, subsequently smoothed by a 1000μF capacitor. Consequently, the output from the capacitor is 12V unregulated DC, serving as input to the IC 7805 voltage regulator. This regulator transforms the input into regulated 5V DC, obtainable at its output terminals.

In this circuit, the input voltage must exceed the output voltage. Input and output currents are approximately equivalent. When a 7.5V 1A supply is applied at the input, the output stabilizes at 5V 1A. Any surplus power is dissipated as heat through the 7805 IC.

Heat Dissipation in 7805 IC

In this type of regulator, a substantial amount of energy is dissipated through heat. The discrepancy between the input and output voltages results in heat generation. Consequently, if the voltage difference is significant, it leads to elevated heat production. To mitigate this, a heat sink is employed with the IC 7805, as excess heat could otherwise lead to operational issues.

7805 IC Heating Problem

The 7805 voltage regulator exhibits inefficiency and dropout voltage issues, resulting in substantial heat dissipation. Proper calculation of heatsink dimensions is essential when employing a heatsink. The following formula aids in determining the suitable heatsink size for such scenarios:

Heat generated = (input voltage – 5) x output current

For instance, in a system with a 15-volt input and a required output current of 0.5 amperes:

Then we have (15 – 5) x 0.5 = 10×0.5 =5W;

Thus, 5 watts of energy are dissipated as heat, necessitating an appropriately sized heatsink for heat dissipation. However, the energy effectively utilized is only (5 x 0.5Amp) = 2.5W.

This implies that twice the energy consumed is wasted as heat. Conversely, if a 9V input is provided under the same load conditions:

(9-5) x 0.5 = 2W

In this scenario, 2 watts of energy would be dissipated as heat.

What should We do Then?

Keep in mind that a higher input voltage results in reduced efficiency for your IC7805.

An optimal input voltage is approximately 7.5V.

Why do We Use Capacitors with 7805?

If the distance between your voltage regulator and the power supply exceeds 25cm (10 inches), it is advisable to incorporate capacitors to filter out residual AC noise. Voltage regulators operate most effectively when supplied with a clean DC signal. Bypass capacitors play a crucial role in reducing AC ripple.

Essentially, these capacitors short out AC noise from the voltage signal, permitting only DC voltage to reach the regulator. While including the two capacitors is not mandatory and can be omitted if line noise is not a concern, they prove valuable in scenarios demanding a pristine DC line, such as mobile phone chargers or logic assessments. Capacitors excel at optimizing voltage regulation, and their values can be slightly adjusted.

How to Get Constant DC Power Supply from AC?

While batteries can serve as an input to the 7805 Voltage Regulator IC, challenges arise, including the recurrent discharge of batteries and a gradual decline in voltage levels over time.

A preferable alternative is to furnish the 7805 Voltage Regulator IC with an unregulated yet rectified DC voltage derived from an AC source. Given the available AC mains supply, a circuit can be devised to convert AC mains to DC, offering it as input to the 7805 Voltage Regulator IC.

Circuit Diagram

The illustration depicts the circuit diagram for generating a regulated 5V from an AC mains power source.

Components Required

• 230V to 12V Step-Down Transformer

• Bridge Rectifier (or 4 PN Diodes – 1N4007)

• 1A Fuse

• 1000μF Capacitor

• 7805 Voltage Regulator IC

• 0.22μF Capacitor

• 0.1μF Capacitor

• 1N4007 Diode

Working

The circuit operates in two stages to transform AC power from the mains into a consistent regulated DC. Comprising a transformer, a bridge rectifier assembled from diodes, a linear voltage regulator (7805), and capacitors, the circuit's functionality unfolds as follows.

In the initial stage, the AC mains convert into unregulated DC, while the subsequent stage refines this unregulated DC into a stable 5V DC. The process begins with a 230V to 12V step-down transformer, where the primary connects to the mains supply and the secondary links to a bridge rectifier (utilizing either a dedicated IC or a combination of four 1N4007 diodes).

A 1A fuse is strategically placed between the transformer and the bridge rectifier to limit the circuit's current draw to 1A. The rectified DC from the bridge rectifier undergoes smoothing with a 1000μF capacitor. Consequently, the output across the 1000μF capacitor yields unregulated 12V DC, serving as input to the 7805 Voltage Regulator IC.

The 7805 IC transforms this input into regulated 5V DC, obtainable at its output terminals. This staged process ensures a reliable and stable regulated DC output.

Important Points on 7805 Voltage Regulator IC

• An essential consideration is that the input voltage should consistently exceed the output voltage by at least 2.5V. The input and output currents are nearly equivalent. 

• For instance, providing a 7.5V 1A supply at the input will yield a 5V 1A output. 

• The surplus power is dissipated as heat, necessitating the utilization of a heat sink, as depicted below, in conjunction with the 7805 IC.

Advantages

The 7805 voltage regulator IC boasts several advantages, including:

It requires no additional components to manage its output voltage.

It incorporates built-in protection mechanisms to safeguard against overvoltage.

A heat sink can be applied via the GND terminal to shield the IC from high currents or short circuits.

7805 Voltage Regulator Applications

• Stable +5V output regulator for powering microcontrollers and sensors across various projects.

• Regulator with a fixed output.

• Positive voltage regulator configured for negative voltage.

• Customizable output regulator.

• Current limiter designed for specific applications.

• Regulator for controlling current.

• Customizable DC voltage regulator.

• Regulated dual-supply system.

• Circuit ensuring protection against output polarity reversal.

• Circuit providing protection against reverse bias.

The 7805 Voltage regulator is employed in constructing circuits for inductance meters, phone chargers, portable CD players, infrared remote control extensions, and UPS power supply circuits. Additionally, we developed a Stopwatch Circuit utilizing the IC7805.

7805 IC Package

LM7805 Datasheet

Download 7805 Datasheet PDF.

Conclusion

The 7805 IC plays a crucial role in circuits susceptible to voltage fluctuations. It is applied across diverse electronic circuits to furnish a consistent output voltage for varying input voltages, making it versatile for various electronic projects. The terminology of the IC is significant, with '78' indicating a positive voltage regulator and '05' specifying a 5V output. Consequently, the IC delivers a +5V output voltage. With integrating a few external components, one can explore and experiment with this regulator in a project of their preference.

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