The7805 Voltage Regulator IC is a commonly usedvoltage regulator that finds its application in most of the electronics projects. It provides a constant +5V output đầu ra voltage for a variable input đầu vào voltage supply.
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LM7805 Pinout Configuration
Pin Number | Pin Name | Description |
1 | Input (V+) | Unregulated input đầu vào Voltage |
2 | Ground (Gnd) | Connected to Ground |
3 | Output (Vo) | Outputs Regulated +5V |
7805 Regulator Features
5V Positive Voltage RegulatorMinimum đầu vào Voltage is 7VMaximum input Voltage is 25VOperating current(IQ) is 5m
AInternal Thermal Overload và Short circuit current limiting protection is available.Junction Temperature maximum 125 degree Celsius
Available in TO-220 và KTE package
Note:Complete Technical Details can be found at the 7805 datasheet given at the over of this page.
Other Voltage Regulators
LM7806, LM7809, LM7812, LM317, LM7905, LM7912, LM117V33, XC6206P332MR.
Brief description of 7805 Voltage Regulator IC
Voltage regulators are very common in electronic circuits. They provide a constant đầu ra voltage for a varied input đầu vào voltage. In our case the 7805 IC is an iconic regulator IC that finds its application in most of the projects. The name 7805 signifies two meaning, “78” means that it is a positive voltage regulator và “05” means that it provides 5V as output. So our 7805 will provide a +5V output đầu ra voltage.
The output current of this IC can go up lớn 1.5A. But, the IC suffers from heavy heat loss hence a Heat sink is recommended for projects that consume more current. For example if the input đầu vào voltage is 12V & you are consuming 1A, then (12-5) * 1 = 7W. This 7 Watts will be dissipated as heat.
7805 as +5V Voltage Regulator
This is a typical application circuit of the 7805 IC. We just need two capacitors of vale 33uf and 0.1uf to lớn get this IC working.
The input capacitor 0.33u
F is a ceramic capacitor that đơn hàng with đầu vào inductance problem & the output capacitor 0.1u
F is also a ceramic capacitor that adds to the stability of the circuit. These capacitors should be placed close to the terminals for them lớn work effectively. Also they should be of ceramic type, since ceramic capacitors are faster than electrolytic.
7805 as adjustable output Regulator
This IC can also act as an adjustable output đầu ra voltage regulator, meaning you can also control the đầu ra voltage for your desired value using the below circuit.
Here, the input voltage can be anywhere between 9V-25V, và the output voltage can be adjusted using the value of resistance R1 & R2. The value can be calculated using the below formulae.
Where, Vxx=5, IQ = 5*10-3
7805 Applications
Constant +5V output regulator lớn power microcontrollers và sensors in most of the projectsAdjustable output Regulator
Current Limiter for certain applications
Regulated Dual Supply
Output Polarity-Reversal-Protection Circuit
Voltage sources in a circuit may have fluctuations resulting in not providing fixed voltage outputs. A voltage regulator IC maintains the output voltage at a constant value. 7805 Voltage Regulator, a member of the 78xx series of fixed linear voltage regulators used lớn maintain such fluctuations, is a popular voltage regulator integrated circuit (IC).
The xx in 78xx indicates the output voltage it provides. 7805 IC provides +5 volts regulated nguồn supply with provisions to địa chỉ a heat sink.
7805 Voltage Regulator IC Specifications
Minimum input voltage is 7VMaximum đầu vào Voltage is 35VCurrent rating Ic = 1AMaximum output đầu ra Voltage VMax=5.2V Minimum output đầu ra Voltage VMin=4.8VLM7805 Voltage Regulator Pinout
| Pin No. | Pin | Function | Description |
| 1 | INPUT | Input voltage (7V-35V) | In this sạc pin of the IC positive unregulated voltage is given in the regulation. |
| 2 | GROUND | Ground (0V) | In this pin where the ground is given. This sạc is neutral for equally the input và output. |
| 3 | OUTPUT | Regulated output; 5V (4.8V-5.2V) | The đầu ra of the regulated 5V is taken out at this pin sạc of the IC regulator. |
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As you may have noticed, there is a significant difference between the đầu vào voltage và the output voltage of the voltage regulator. This difference between the input and output voltage is released as heat. The greater the difference between the input và output voltage, more the heat is generated.
If the regulator does not have a heat sink to dissipate this heat, it can get destroyed & malfunction. Hence, it is advisable to limit the voltage to a maximum of 2-3 volts above the output voltage.
So, we now have 2 options. Either design your circuit so that the input voltage going into the regulator is limited to 2-3 volts above the output đầu ra regulated voltage or place an appropriate heatsink, that can efficiently dissipate heat.
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7805 IC Heating Problem
7805 voltage regulator is not very efficient & has drop-out voltage problems. A lot of energy is wasted in the form of heat. If you are going lớn be using a heatsink, better calculate the heatsink kích thước properly. The below formula should help in determining the appropriate heatsink kích cỡ for such applications.
Heat generated = (input voltage – 5) x đầu ra current
If we have a system with an input of 15 volts & the đầu ra current required is .5 amperes,
Then we have: (15 – 5) x 0.5 = 10×0.5 =5W;
5W energy is being wasted as heat, hence an appropriate heatsink is required to lớn disperse this heat. On the other hand, the energy actually being used is: (5 x 0.5Amp) = 2.5W.
So twice the energy, that is actually utilized is wasted. On the other hand, if 9V is given as input at the same amount of load: (9-5) x 0.5 = 2W
2W energy will be wasted as heat.
What should we vày then?Remember… higher the đầu vào voltage, the less efficient your IC7805 will be.
An estimated efficient đầu vào voltage would be about 7.5V.
Why do we use Capacitors with 7805?
If your voltage regulator is situated more than 25cm (10 inches) from the power supply, capacitors are needed to filter residual AC noise. Voltage regulators work efficiently on a clean DC signal being fed. The bypass capacitors help reduce AC ripple.
Essentially, they short AC noise from the voltage signal & allow only DC voltage into the regulator. The two capacitors are not necessarily required và can be omitted if you are not concerned about line noise.
However, for a thiết bị di động phone charger or ngắn gọn xúc tích assessment, you require a nice clean DC line. Capacitors will be beneficial in this case as they are good at maximizing voltage regulation. The values of capacitors can also be changed slightly.
You can check Why Are Filter Capacitors Used In Some Battery Charger Circuits?
Let’s take a look at what makes the IC tick.
7805 Voltage Regulator IC Schematic
The heart of the 7805 IC is a transistor (Q16) that controls the current between the input và output & thus controls the đầu ra voltage. The bandgap reference (yellow) keeps the voltage stable. It takes the scaled output voltage as input đầu vào (Q1 & Q6) và provides an error signal (to Q7) for indication if the voltage is too high or low.
The key task of the bandgap is lớn provide a stable and accurate reference, even as the chip’s temperature changes.
The error signal from the bandgap reference is amplified by the error amplifier (orange). This amplified signal controls the output đầu ra transistor through Q15. This closes the negative feedback loop controlling the output voltage.
The startup circuit (green) provides initial current to lớn the bandgap circuit, so it doesn’t get stuck in an “off” state. The circuit in purple provides protection against overheating (Q13), excessive đầu vào voltage (Q19), & excessive đầu ra current (Q14).
These circuits reduce the đầu ra current or shut down the regulator, protecting it from damage in case of a fault. The voltage divider (blue) scales down the voltage on the đầu ra pin for use by the bandgap reference.
Scaling the Output
The 7805’s scaled output đầu ra provides the input voltage (Vin) lớn the bandgap reference and the bandgap provides an error signal as the output. The 7805’s bandgap circuit removes the feedback loop that exists inside a traditional bandgap reference. Instead, the entire cpu becomes the feedback loop.
If the output đầu ra voltage is correct (5V), then the voltage divider provides 3.75V at Vin. Any change in output đầu ra voltage propagates through quận 6 and R7, causing the voltage at the base of quận 7 to rise or fall accordingly.
This change is amplified by quận 7 and Q8, generating the error output. The error output, in turn, decreases or increases the current through the output transistor. The negative feedback loop adjusts the đầu ra voltage until it is correct.
IC 7805 Voltage Regulator Applications
7805 IC is used in a wide range of circuits. The major ones are:
Fixed-Output RegulatorPositive voltage Regulator in Negative voltage Configuration
Adjustable output Regulator
Current Regulator
Adjustable DC Voltage Regulator
Regulated Dual-Supply
Output Polarity-Reversal-Protection Circuit
Reverse bias projection Circuit
7805 Voltage regulator also finds usage in building circuits for inductance meters, phone chargers, portable CD player, infrared remote control extension, and UPS nguồn supply circuits. Also, we designed a Stopwatch Circuit using IC7805.
