7805 voltage regulator


The voltage regulator is the important part of a power supply circuit, stability of the power provided to the device is a concern, so in this article, we are going to explain a very common voltage regulator component called 7805.

We are expecting to make a 7805 all in one post, learn about every important information’s of 7805 voltage regulator ICs, in the lights of this, we include topics of 7805 such as pin diagram, internal circuit diagram, and small explanation, voltage, and other ratings, different circuits using 7805, applications.

7805 voltage regulator
7805 voltage regulator

7805 pinout diagram 


7805 pinout diagram
7805 pinout diagram

The 7805 is a three-terminal voltage regulator IC, counting the terminals from left to right, 1st terminal pin is input, here we were given the unregulated signal and 2nd terminal pin is the regulator device ground port, and the 3rd terminal pin is the output port.

The name 7805 also indicates some information’s about the voltage regulator device, first two digits that is “78” indicate that the voltage regulator is a positive type and the last two digits “05” indicate its voltage rating, here it is +5v.


Pin Number Pin Name Description
1 Input (V+) Unregulated Input Voltage
2 Ground (Gnd) Connected to Ground
3 Output (Vo) Outputs Regulated +5V


7805 Features

1.   3-Terminal Regulators

2.   Output Current up to 1.5 A

3.   Internal Thermal-Overload Protection

4.   High Power-Dissipation Capability

5.   Internal Short-Circuit Current Limiting

6.   Output Transistor Safe-Area  Compensation

7.   5V Positive Voltage Regulator

8.   Minimum Input Voltage is 7V

9.   Maximum Input Voltage is 25V


Internal circuit diagram of 7805 

Internal circuit diagram of 7805
Internal circuit diagram of 7805
We know an integrated voltage regulator device is a combination of multiple circuit networks with integration of different functions, here is try to explain most of the informations about the internal circuit of 7805 ICs.
  • The main aim of this 7805 network is to provide a stable and accurate reference, even the temperature varies.
  • This circuit is capable of reducing the output current or shut down the regulator
  • We start with the input block, they are used to provide input current to the block. (green)
  • At the output portion of the input block, we are using a (purple) Q13 transistor for protection against overheating.
  • The next block that is (yellow) is the main component, which is used to stabilize the voltage, Q1 and Q6 regulate the voltage and pass to the next block (orange), Q7 provides you an error signal for the indication if the voltage is too high or low.
  • The reference signal or error signal from the block is amplified by the error amplifier at the (orange block).
  • A portion of (orange block) is the feedback element, which is Q15, this network completes the negative feedback component and is used to control the output voltage.
  • And then (green block) is a voltage divider, which is used to drop down the voltage on the output used by the reference. 

Voltage specifications of 7805 IC


A 7805 voltage regulator can deliver fixed positive 5v output, the voltage range we can provide at the input is enormous such as 7v to 35v.

But the voltage regulator didn’t provide you a fixed voltage or the device manufactured with a variation of 5.2v to 4.8v is shown by the 7805 regulators.


current specifications of 7805 IC


The 7805 regulators ICs did not have a higher value of the current rating, the data’s from the 7805 IC datasheet indicated that 1-1.5amps of current must delivered and further higher values of current will be delivered with the modification made at the circuit.

7805 Heating problem 


Whenever we come across the heating problems of 7805 voltage regulator ICs, we need to know it is a very common thing in such a power supply type.

The power dissipation at a linear voltage regulator is the working operation done to produce the desire output voltage.

The input and output voltage ranges will be maintained by dropping the excess voltages in the form of heat.

 The linear voltage is also called dissipation voltage regulators, due to its connection, it connects series with the load.

Using this formula, we are calculating the heat dissipation 

V IN –V Out * I out  

The equation states that the difference between input voltage (V in) and output voltage (V out) and then the amount of current, which is drawn from the regulator, larger the voltage difference (Vin-V out) shows the higher power dissipation.

These are the reason why heat sinks are the main component at the normal operation of the 7805 voltage regulator.  


Basic circuit of 7805 

basic circuit of 7805
basic circuit of 7805

The circuit shows the basic voltage regulator circuit using 7805, circuit only has three components input capacitor C1 is a ceramic capacitor type used to deal with input impedance.

And next output capacitor C2 also a ceramic capacitor, that is added for the stability of the circuit.

The ceramic capacitors are recommended at this circuit, for faster operation.


7805 Adjustable voltage regulator  


7805 Adjustable voltage regulator
7805 Adjustable voltage regulator

The adjustable function is not available in the 7805 voltage regulator, normally linear voltage regulators functioned as, make a fixed voltage at the output and dissipate excess power into heat.

Here at the 7805 adjustable regulators, we have only very few components for functions the 7805 as an adjustable voltage regulator, the circuit only have four components, at input we have C1 capacitor for input impedance and C2 capacitor for stability, then at output R1 fixed resistor and R2 variable resistor, this forms a voltage divider network at the output.

In this circuit 2nd pin, the ground is taken as an adjustable pin, the ground pin is used to properly closes the circuit and acts as regulator component and voltage varies concerning varying the variable resistor at the output.


7805 High current voltage regulator 


7805 High current voltage regulator
7805 High current voltage regulator

The circuit below is a high current voltage regulator, normally 7805 voltage regulator circuit deliver around 1amps of current, but this particular transistor-based voltage regulator circuit is capable of delivers 4amps of current in its output.


The power transistors are used to supply an extra bit of current to the load of the regulator, these transistors had a known as outboard bypass transistor.


When the input signal reaches resistor R1 and develops a voltage which is to power up the power transistor, the transistor delivers high amps of current, and 7805 regulated the voltage difference.


At the output, the signal is a combination of 7805 voltage regulated signal and high amps of transistor signal.


7805 High output current with short circuit protection 

7805 High output current with short circuit protection
7805 High output current with short circuit protection


The circuit above is also the same high current circuit using 7805 voltage regulator and transistor, only difference is the extra feature called short circuit protection. 

The short circuit protection feature is done with an extra transistor also called a complementary transistor, working of the circuit is almost similar to the high current circuit.

When the input signal approaches the circuit and both the transistors have a base resistor, as soon as the voltage on R1 and Rsc becomes higher than 0.6 – 0.7v.

This leads to turning ON transistor Q1 and high current raises, short circuit protection function start act by reducing the maximum current consumption when the output voltage drops.

The short circuit occurs, the power dissipation can be very high.


Advantage of 7805 


  • The 7805 voltage regulator have protection systems
  • The 7805 voltage regulator have very few external components
  • High current circuit application capability 
  • They have applications in higher and lower frequency sensitive circuits, such as an amplifier.


Disadvantage of 7805 


  • The 7805 voltage regulator circuit has a minimum limit in its input voltage (around 2.5v) than the output voltage.
  • The circuit is heavier than switching circuits.
  • The efficiency of the circuit is lower due to power dissipation by heat (larger heat sinks are a must thing.)

Applications of 7805 


  • 7805 voltage regulator provides +5v constant voltage, so this will be the right option for microcontrollers, sensors, and Arduino boards.
  • The 7805 regulator is capable of works as adjustable output regulators (the ground pin at the 7805 IC will act as an adjustable pin.)
  • The 7805 voltage regulator works as dual power supplies.
  • Phone charger circuits.
  • Bench power supplies
  • Current regulator circuits
  • Inductance meters 
  • Reversal protection circuits

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