7805 where applicable. Scheme of connecting the stabilizer L7805CV, description of characteristics. Current source circuit made on microcircuits from the L78xx series
L7805-CV- for almost any radio amateur, it is not difficult to assemble a power supply with a stabilizing output voltage on a 7805 chip and similar ones from this series. It is this linear input DC voltage regulator that will be discussed in this material.
The figure above shows a typical linear circuit. stabilizer L7805 with positive polarity 5v and rated operating current 1.5A. These microcircuits have gained such popularity that most of the world's companies have taken up their production. But in the picture below, the circuit is slightly improved, by increasing the capacitance of capacitors C1-C2.
As a rule, between radio engineers and electronics engineers, this chip is abbreviated, without naming the letters in front of it indicating the manufacturer. After all, it is already clear to everyone that this is a stabilizer, the last digit, which is indicated by its output voltage.
For those who have not yet encountered these electronic components in practice and know little about them, here is a short video on assembling the circuit for clarity:
Voltage stabilizer 5v! On the L7805CV chip
One of the important conditions is the high quality of the components
In fact, when buying components, the manufacturer plays a significant role. When you purchase any electronic components, always pay attention to the brand of the part and ask who supplies it. Personally, I am satisfied with the products of STMicroelectronics, a manufacturer of microelectronic components.
Nameless stabilizers or from little-known companies, as a rule, are always cheaper than similar ones from well-known brands. But the quality of such parts is not always at the proper level, the significant spread of the output voltage especially affects their work.
In fact, I have come across many chips L7805 giving out output voltage within 4.6v, instead of 5v, while others from the same series gave, on the contrary, more - 5.3v. In addition, such samples can often create a decent background and increased power consumption.
Current source circuit made on microcircuits from the L78xx series
The value of the output current is determined by the constant resistor R* connected in parallel with the 0.1uF capacitor, it is this resistance that, in turn, creates a load for L7805. Moreover, the stabilizer has no grounding. Only one output of the load resistance Rn goes to the "ground". The principle of operation of such a switching circuit obliges the L7805-CV to deliver a certain amount of current to the load by regulating the output voltage.
The value of the current at the output of the source L78хх
An unpleasant moment that can be observed in the circuit is the summation of the quiescent current Id with the output current. The parameters of the quiescent current are indicated in the documentation for the microcircuit. Basically, such stabilizers have a constant quiescent current of 8mA. This value is the lowest output circuit current of the chip. Therefore, when trying to create a current source whose value is less than 8mA, it will not work.
Here you can download the documentation for the L78xx chip
At best, the L7805 can produce output currents ranging from 8mA to 1A. However, when operating at currents exceeding 750-850 mA, we strongly recommend installing the microcircuit on a radiator. But to work on such currents is still not justified. The current of 1A indicated in the documentation is its maximum value. Under actual conditions, the chip is likely to fail due to overheating. Therefore, the optimal output operating current should be between 20 mA and 750 mA.
Output current correctness and voltage value
At the same time, the non-constancy of the quiescent current is formed as ΔId = 0.5mA. This value indicates the accuracy of the current setting in the output path. Accordingly, the accuracy of setting the output current depends on the load resistance of the microcircuit R*. In this case, it is desirable to use precision resistors having high stability and significant accuracy, from ±0.0005% to ±0.5%.
Optimal load resistance
At the same time, the value of the load resistance must be taken into account. Everything is simple here, that is, using Ohm's law, you can calculate everything. For example:
V= I*R = 0.1 * 100 = 10 Volts
Based on such simple calculations, we found out what voltage should be across a load with a resistance of 100 ohms in order to create an output current of 100 mA. According to these calculations, it turns out that the best option would be to use a 7812 or 7815 chip, rated for 12v and 15v in accordance, in order to have a margin.
Conclusion
Naturally, there are limiting moments in such a current source circuit. Although it can be useful for a large number of solutions in which high accuracy does not play a special role. The absence of any complexity in the circuit makes it possible to manufacture a current source in almost any conditions, especially since it will not be difficult to purchase components for it.
Devices that are included in the power supply circuit and maintain a stable output voltage are called voltage stabilizers. These devices are designed for fixed output voltages: 5, 9 or 12 volts. But there are devices with the presence of regulation. In them, you can set the desired voltage within certain available limits.
Most stabilizers are designed for a certain maximum current that they can withstand. If this value is exceeded, the stabilizer will fail. Innovative stabilizers are equipped with a current blocking, which ensures that the device turns off when the maximum current in the load is reached and are protected from overheating. Along with stabilizers that support a positive voltage value, there are also devices that operate with a negative voltage. They are used in bipolar power supplies.
The 7805 stabilizer is made in a package similar to a transistor. The figure shows three conclusions. It is designed for a voltage of 5 volts and a current of 1 ampere. There is a hole in the case for fixing the stabilizer to the radiator. Model 7805 is a positive voltage device.
The mirror image of this regulator is its counterpart 7905, designed for negative voltage. There will be a positive voltage on the case, a negative value will go to the input. -5 V is removed from the output. In order for the stabilizers to work in normal mode, 10 volts must be applied to the input.
Pinout
The 7805 stabilizer has a pinout, which is shown in the figure. The common terminal is connected to the body. During the installation of the device, this plays an important role. The last two digits indicate the voltage output by the microcircuit.
Microcircuit Power Stabilizers
Consider the methods of connecting to the power of digital devices made independently on microcontrollers. Any electronic device requires a proper power connection to function properly. The power supply is designed for a certain power. At its output, a capacitor of a significant capacitance is installed to equalize the voltage pulses.
Power supplies without stabilization, used for routers, cell phones and other equipment, cannot be directly combined with the power supply of microcontrollers. The output voltage of these units varies and depends on the connected power. An exception to this rule are charging blocks for smartphones with a USB port that outputs 5 V.
The scheme of the stabilizer, combined with all microcircuits of this type:
If you disassemble the stabilizer and look at its insides, then the circuit would look like this:
For electronic devices that are not sensitive to voltage accuracy, such a device is suitable. But for precise equipment, a high-quality circuit is needed. In our case, the 7805 stabilizer outputs a voltage in the range of 4.75-5.25 V, but the current load should not exceed 1 A. The unstable input voltage fluctuates in the range of 7.5-20 V. In this case, the output value will be constantly equal to 5 B. This is the advantage of stabilizers.
With an increase in the load that the microcircuit can produce (up to 15 W), it is better to provide the device with cooling by a fan with an installed radiator.
Workable stabilizer circuit:
Technical data:
- The highest current is 1.5 A.
- The input voltage range is up to 40 volts.
- Output - 5 V.
In order to avoid overheating of the stabilizer, it is necessary to maintain the lowest input voltage of the microcircuit. In our case, the input voltage is 7 volts.
The microcircuit dissipates the excess power on itself. The higher the input voltage on the chip, the higher the power consumption, which is converted into case heating. As a result, the microcircuit will overheat and the protection will work, the device will turn off.
Voltage stabilizer 5 volts
Such a device differs from similar devices in its simplicity and acceptable stabilization. It uses the K155J1A3 chip. This stabilizer was used for digital devices.
The device consists of working units: a start-up, a reference voltage source, a comparison circuit, a current amplifier, a transistor switch, an inductive energy storage device with a diode switch, input and output filters.
After the power is connected, the start-up unit, which is made in the form of a voltage stabilizer, begins to operate. A voltage of 4 V appears on the emitter of the transistor. Diode VD3 is closed. As a result, the exemplary voltage and current amplifier are turned on.
The key on the transistors is closed. A voltage pulse is generated at the output of the amplifier, which opens a key that passes current to the energy storage device. The stabilizer turns on the negative connection circuit, the device goes into operation mode.
All used parts are carefully checked. Before installing a resistor on the board, its value is made equal to 3.3 kOhm. The stabilizer is first connected to 8 volts with a load of 10 ohms, then, if necessary, set it to 5 volts.
The voltage stabilizer is the most important radio element of modern radio-electronic devices. It provides a constant voltage at the output of the circuit, which is almost independent of the load.
Stabilizers of the LM family
In our article, we will consider voltage stabilizers of the LM78XX family. Series 78XX is available in TO-3 metal cases (left) and TO-220 plastic cases (right). Such stabilizers have three outputs: input, ground (common) and output.
Instead of “XX”, manufacturers indicate the stabilization voltage that this stabilizer will give us. For example, a 7805 stabilizer will output 5 volts at the output, 7812, respectively, 12 volts, and 7815 - 15 volts. Everything is very simple.
Wiring diagram
And here is the wiring diagram for such stabilizers. This circuit is suitable for all stabilizers of the 78XX family.
Characteristics of LM Stabilizers
What voltage should be applied so that the stabilizer works as it should? To do this, we are looking for a datasheet for stabilizers and carefully studying it.We are interested in these features:
output voltage- output voltage
input voltage- input voltage
We are looking for our 7805. It gives us an output voltage of 5 volts. Manufacturers noted a voltage of 10 volts as the desired input voltage. But, it happens that the output stabilized voltage is sometimes either slightly underestimated or slightly overestimated. 
For electronic knickknacks, fractions of volts are not felt, but for precision (accurate) equipment, it is still better to assemble your own circuits. Here we see that the 7805 stabilizer can give us one of the voltages in the range of 4.75 - 5.25 Volts, but the conditions must be met that the current at the output in the load will not exceed 1 Ampere. An unstabilized DC voltage can “fluctuate” in the range from 7.5 to 20 Volts, while the output will always be 5 Volts.
The dissipated power on the stabilizer can reach up to 15 watts - this is a decent value for such a small radio component. Therefore, if the load at the output of such a stabilizer will eat a decent current, I think you should think about cooling the stabilizer. To do this, it must be planted through the KPT paste on the radiator. The greater the current at the output of the stabilizer, the larger the radiator should be. It would be generally ideal if the radiator was still blown by a fan.
LM work in practice
Let's look at our ward, namely, the LM7805 stabilizer. As you already understood, at the output we should get 5 volts of stabilized voltage.
Let's assemble it according to the scheme
We take our Breadboard and quickly assemble the above proposed connection diagram. Two yellow ones are capacitors, although it is not necessary to install them.
So, wires 1,2 - here we drive an unstabilized input DC voltage, remove 5 Volts from wires 3 and 2.
On the Power Supply, we set the voltage in the range of 7.5 Volts and up to 20 Volts. In this case, I set the voltage to 8.52 Volts.
And what did we get at the output of this stabilizer? 5.04 Volts! This is the value we get at the output of this stabilizer if we apply voltage in the range from 7.5 to 20 Volts. Works great!
Let's check one more of our stabilizers. I think you have already guessed how many volts it is.
We collect it according to the scheme above and measure the input voltage. According to the datasheet, you can apply an input voltage from 14.5 to 27 Volts to it. We set 15 Volts with kopecks.
And here is the output voltage. Damn, some 0.3 volts is not enough for 12 volts. For radio equipment operating from 12 volts, this is not critical.
How to make a power supply for 5, 9.12 Volts?
How to make a simple and highly stable power supply for 5, 9 or even 12 volts? Yes, very simple. To do this, you need to read this article and put a stabilizer on the radiator at the output! And that's it! The circuit will be approximately like this for a 5 Volt power supply:
Two electrolytic capacitors to eliminate ripple and a highly stable 5 volt power supply at your service! To get a power supply for a higher voltage, we also need to get a higher voltage at the output of the transformer. Strive for the voltage on the capacitor C1 to be no less than in the datasheet for the described stabilizer.
In order for the voltage regulator not to overheat, apply the minimum voltage specified in the datasheet to the input. For example, for a 7805 regulator, this voltage is 7.5 volts, and for a 7812 regulator, a voltage of 14.5 volts can be considered a desirable input voltage. This is due to the fact that the voltage difference, and hence the power, the stabilizer will dissipate on itself.
As you remember, the formula for power is P=IU, where U is voltage and I is current. Therefore, the greater the input voltage of the stabilizer, the greater the power consumed by it. And excess power is heating. As a result of heating, such a stabilizer can overheat and enter a protection state, in which further operation of the stabilizer stops or even burns out.
Conclusion
An increasing number of electronic devices require high-quality stable power without any power surges. Failure of one or another module of electronic equipment can lead to unexpected and not very pleasant consequences. Use the achievements of electronics to your health, and do not worry about the power of your electronic knick-knacks.
Buy voltage stabilizer
You can buy these integrated stabilizers cheaply as a whole set on Aliexpress at once. this
link. There are absolutely any values here, even for negative voltage.
I converted the speaker amplifier to a penny D-class module on the PAM8403. The speakers began to play louder, a type of bass appeared. Satisfied. But there was one problem - if you supply power to the speakers from the usual (pulse) charging at 5V, there were large distortions in the power supply. At a low volume it was still possible to listen, at a high volume it was impossible. I decided to solder the power supply with linear stabilization.
The scheme of such a PSU is simple:
The first impulse is to buy all the details in the local "Electronics" and quickly solder the power supply circuit on the breadboard. I calculated only the price of stabilizer parts - it turned out about 700 rubles. The toad choked. Let's look at ready-made options on Ali and ebee. Everything here is chocolate. There are penny designers (to solder on the printed circuit board yourself), there are ready-made modules for 110 rubles. I ended up buying it on eBay, it was cheaper there. It's been three weeks. The stabilizer dangled on the radiator - screwed it tight. 
The rest of the details are a transformer, a fuse, a case, a power button, legs for the case, a usb connector in Electronics. It took 500 rubles for everything.
Characteristics of the module and stabilizer LM7805:
1. Board size. 57mm*23mm
2. Input voltage input voltage polarity, AC and DC can, range. 7.5-20V
3. The output voltage 5V
4. The maximum output current. 1.2A
5. Provided fixed bolt hole, convenient installation
As you can see, voltage from 7.5V to 20V can be applied to the module. The output is 5V.
The stabilizer inside is quite complicated: 
The transformer bought such a TP112 (7.2 W) 2 * 12V xx - 
I took the power button for 220 V - quite large. 
Button with fixation and backlight. How to connect the backlight when pressed - I did not understand (can you tell me, who knows?). I did it without backlight. 
Assembled a stand for testing: 
Speakers play without distortion at maximum volume. Nothing in the PSU gets very hot. Goal achieved: 
I tried to charge the phone - current 0.5A 
With a 1 A resistor, everything is quite sad: 
Conclusion - this power supply cannot be used as a charger. Apparently the transformer needs to be put more powerful.
Putting it all together: 
I made a hole on top in order to see the LED - an indicator on the module to indicate operation. On the reverse side, the hole was sealed with a transparent film.
Thank you for your attention.
I plan to buy +14 Add to favorites Liked the review +23 +38Regulated supply voltage is very important for many electronic devices, because the semiconductor components used in them can be sensitive to surges and unregulated voltage noise. Mains-powered electronic devices first convert the AC voltage to DC through a diode bridge or other similar element. But this voltage should not be used in sensitive circuits.
In this case, you need a voltage regulator (or stabilizer). And one of the most popular and common regulators today is the 7805 series regulator.
The 7805 chip is housed in a three-terminal TO-220 package with input, output, ground (GND) pins. Also, the GND contact is presented on the metal base of the microcircuit for mounting the radiator. This stabilizer supports an input voltage of up to 40 V, and provides 5 V at the output. The maximum load current is 1.5 A. The appearance of the voltage regulator 7805 with the pinout is shown in the image below.
Thanks to the 7805 series voltage stabilizer, the output is fixed at a certain level without perceptible surges and noise. In order to effectively minimize output noise and make the output voltage as stable as possible, the 7805 regulator must be properly “tied”, that is, blocking, smoothing capacitors must be connected to its input and output. The diagram for connecting capacitors to the 7805 (U1) chip is shown below.
Here capacitor C1 is a bypass or blocking capacitor and is used to damp very fast input surges to ground. C2 is a filter capacitor that allows you to stabilize slow changes in input voltage. The larger its value, the greater the level of stabilization, but you should not take this value too high if you do not want it to discharge longer after switching on. Capacitor C3 also stabilizes slow voltage changes, but at the output. Capacitor C4, like C1, dampens very fast surges, but after the regulator and immediately before the load.
A typical wiring diagram for the 7805 voltage regulator is shown below. Here, the alternating voltage is rectified by a diode bridge and fed to the regulator with the required piping of capacitors for better stabilization of the output voltage. Diode D5 is also added to the circuit to avoid a short circuit and thus secure the regulator. If it weren't there, then the output capacitor would have a chance to quickly discharge during the low impedance period inside the regulator.
Thus, the voltage regulator is a very useful element in the circuit, able to provide proper power to your device.