Voltage Source

The voltage source is a device that produces a precise output voltage that theoretically does not change regardless of the load current.

We found that there are two types of elements in an electrical or electronic circuit : passive elements and active elements.The active element is the element that can continuously provide energy to a circuit such as battery, generator, operational amplifier, etc. Passive elements are physical elements such as resistors, capacitors, inductors, etc. it cannot produce electrical energy on its own, it just consumes it.

The most important for us are the types of active circuit elements, which provide electrical energy to the connected circuits or networks.These are called "electrical sources" with two types of electricity sources, voltage source and current source.The current source is usually less common in circuits than the voltage source, but both are used and can be considered complementary to each other.

An electrical source, or simply a "source", is a device that provides electrical power to a circuit in the form of a voltage source or a current source.Both types of electrical sources can be classified as a direct (DC) or alternative (AC) source, in which a constant voltage is called the DC voltage and over time it changes sinusoidally.Batteries, for example, are DC sources, and the 230V wall socket or power outlet in your home is an AC source.

We have previously said that electricity sources provide energy, but one of the interesting features of an electricity source is that they can convert non-electric energy to electrical energy or vice versa.For example, a battery converts chemical energy into electrical energy, while an electric machine such as a DC generator or AC alternator converts mechanical energy into electrical energy.

Renewable technologies can convert energy from solar, wind and waves into electricity or thermal energy.However, electricity sources can both transmit and absorb energy, allowing it to flow in both directions, in addition to converting energy from one source to another.

Another important feature that defines the operation of an electrical source and its operation is its IV properties.The IV property of an electrical source can give us a very beautiful illustrated description of the source as a voltage source and a current source, as shown.

Electrical Resources

Voltage Source

Electrical sources can be classified as independent (ideal) or dependent, (controlled) both as a voltage source and as a current source; the value depends on a voltage or current elsewhere in the circuit and may change or be constant over time.

When dealing with circuit rules and analysis, electrical sources are often considered "ideal", that is, the source is ideal because theoretically it can transmit an infinite amount of energy without loss and therefore have properties represented by a straight line.However, in real or practical sources, there is always a parallel connected resistance for a current source or a serially connected resistance for a voltage source associated with the source affecting its output.

Voltage Source

A voltage source, such as a battery or generator, provides a potential difference (voltage) between two points within an electrical circuit that allows the current to flow around.Keep in mind that voltage can also exist without current.A battery is the most common source of voltage for a circuit called voltage terminal voltage, which appears in the positive and negative terminals of the source.

Ideal Voltage Source

Voltage Source

An ideal voltage source is defined as (i) a two-terminal active element capable of maintaining and maintaining the same voltage throughout its terminals, regardless of the current passing through it.In other words, an ideal voltage source will always provide a constant voltage, regardless of the value of the supplied current, which produces an IV characteristic represented by a straight line.

Then an ideal voltage source is known as the Independent Voltage Source, since its voltage does not depend on the value or direction of the current passing through the source, it is determined only by the value of the source.For example, a car batteryhas a terminal voltage of 12V, which remains constant as long as the current passing through it does not rise, provides power to the vehicle in one direction and absorbs power in the other direction while charging.

On the other hand, a Dependent Voltage Source or a controlled voltage source provides a voltage source whose size depends either on the voltage on it or the current passing through another circuit element.A dependent voltage source is indicated in the shape of a diamond and is used as equivalent electrical sources for many electronic devices such as transistors and operationalamplifiers.

Connecting Voltage Sources Together

Ideal voltage sources can be connected both parallel and serial, as with any circuit element.When adding serial voltages to each other, parallel voltages have the same value.Keep in mind that the ideal unequal voltage sources cannot be connected directly to each other in parallel.

Parallel Voltage Source

Voltage Source

Although it is not the best application for circuit analysis, ideal voltage sources can be connected in parallel, provided that they are of the same voltage value.In this example, two 10 volt voltage sources are combined to produce 10 volts between terminals A and B. Ideally, there would be a single voltage source of 10 volts between terminals A and B.

It is to connect the ideal voltage sources with different voltage values, as shown, which is not allowed or is not best practice, or short-circuited by an external closed loop or branch.

Poorly Connected Voltage Sources

Voltage Source

However, when dealing with circuit analysis, Kirchoff's Voltage Act can use voltage sources of different values, provided that there are other circuit elements between them, to comply with the KVL.

Unlike parallel connected voltage sources, ideal voltage sources of different values can be connected in series to create a single voltage source, the output of which will be algebraically collected or removed.Their connection can be as follows: serial auxiliary or serial opposite voltages, as shown.

Serial Voltage Source

Voltage Source

Serial auxiliary voltage sources are serially connected sources so that the poles are connected so that one plus terminal is connected to the negative terminal of the next, allowing the current to flow in the same direction.In the example above, two voltages of 10V and 5V of the first circuit can be added for a V S of 10 + 5 = 15V.So the voltage in terminals A and B is 15 volts.

Serial counter voltage sources, polarity, plus terminal or negative terminals are serially connected sources that are connected to each other as shown in the second circuit above.The clear result is the removal of tensions.Then, the two voltages of 10V and 5V of the second circuit are removed by removing the smaller voltage from the larger voltage.Results in a V S of 10 – 5 = 5V.

The polarity between terminals A and B is determined by the greater polarity of voltage sources, in this example terminal A is positive and terminal B is negative and results in +5 volts.If the serial opposite voltages are equal, the net voltage in A and B will be zero, as one voltage balances the other.In addition, any current (I) will be zero, since the current cannot flow without any voltage source.

Voltage Source Question Sample 1

To provide a load resistance of 100 Ohms, the two series are connected, helping with ideal voltage sources of 6 volts and 9 volts respectively.

calculate the welding voltage, V S , load current passing through the resistance, total power spent by I R and resistance, P and draw the circuit:

Voltage Source

Thus, V S = 15V, I R = 150mA or 0.15A and P R = 2.25W.

Practical Voltage Source

We found that an ideal voltage source can provide a voltage source independent of the current passing through it, that is, it always maintains the same voltage value.This idea may work well for circuit analysis techniques, but in the real world voltage sources behave slightly differently from a practical voltage source, the terminal voltage will actually decrease with an increase in the load current.

Since the terminal voltage of an ideal voltage source does not change with increases in load current, this means that an ideal voltage source has zero internal resistance, R S = 0. In other words, it is a source of voltage without resistance.In reality, all voltage sources have a very small internal resistance, which reduces terminal voltages because they provide higher load currents.

For non-ideal or practical voltage sources such as batteries, the elements that are connected as shown in the internal resistance (R S) create the same effect as a serially connected resistance with an ideal voltage source in these two series carrying the same current.

Ideal and Practical Voltage Source

Voltage Source

You may have noticed that a practical voltage source is very similar to the equivalent circuit of Thevenin, since thevenin theorem "resistors and any linear network containing emk and current sources can be replaced with a single voltage source, V S can be serially replaced with a single voltage source. resistance, R S ".Note that if the serial welding resistance is low, the voltage source is ideal.When the welding resistance is infinite, the voltage source is open circuit.

In the case of all real or practical voltage sources, this internal resistance has an effect on the IV property of the source, as the terminal voltage decreases with an increase in the load current, no matter how small the R S.This is because the same load current flows through the R S.

Ohm law tells us that when a current (i) passes through a resistance, a voltage drop occurs along the same resistance.The value of this voltage drop is given as i*R S.Then V OUT will equal the ideal voltage source, i*R S voltage drop along V S minus resistance.Note that in the case of an ideal welding voltage, the R Sis equal to zero, since there is no internal resistance, so the terminal voltage is the same as the V S.

So, the sum of voltage around the loop given by Kirchoff's voltage law KVL: V OUT = V S – i*R S.This equation can be drawn to give the IV properties of the actual output voltage.As shown, when the current is i = 0, –R S will give a straight line with a slope that cuts the vertical voltage axis at the same point as V S.

Practical Voltage Source Characteristics

Voltage Source

Therefore, opening the whole place with a slight amount of voltage sources will have an IV characteristic, but instead it will be a flat line IV characteristic but not ideal or real practical voltage sources and R* equal to S where R S is internal weld resistance (or impedance).The IV properties of a real battery provide a very close approach to an ideal voltage source, since the welding resistance R S is usually quite small.

The decrease in the angle of inclination of IV characteristics is known as regulation as the current increases.This is an important measure of the quality of the voltage source in the voltage regulation practically as it measures the change of the end voltage between no load = 0, (open circuit) and the maximum when the full load is L, (short circuit).

Voltage Source Question Sample 2

A battery source consists of an ideal voltage source in series with built-in resistance.The voltage and current measured in the battery terminals were V OUT1 = 130V at 10A and V OUT2 = 100V in 25A.Calculate the degree of voltage and the value of the internal resistance of the ideal voltage source.Draw IV characteristics.

First of all, in the form of a simple " simultaneous equation ", let's define the two voltage and current outputs of the battery supply as V OUT1 and V OUT2.

Voltage Source

As in the form of a synchronous equation, we will first multiply V OUT1by five, (5) and V OUT2by two to find the V S, (2) as shown to make the value of the two currents, (i) the same for both equations.

Voltage Source
Voltage Source

Knowing that the ideal voltage source, V S is equal to 150 volts, we can use this value for the V OUT1 (or V OUT2 if desired) equation and solve the serial resistance to find R S .

Voltage Source

Then for our simple example, the internal voltage source of the batteries is calculated as follows: V S = 150 volts and internal resistance: R S = 2Ω.The IV features of the battery are given as follows:

Battery IV Features

Voltage Source

Dependent Voltage Source

Unlike an ideal voltage source that produces a constant voltage between its terminals, regardless of what it depends on, a controlled or dependent voltage source changes the terminal voltage depending on the voltage or passing current opposite another element connected to the circuit, and therefore, if you do not know the true value of the voltage or current to which it is connected, it is sometimes difficult to indicate the value of a dependent voltage source.

Dependent voltage sources behave similarly to the sources of electricity that we have examined so far, both practical and ideal (independent) the difference this time is that a dependent voltage source can be controlled by an input current or voltage.A voltage source connected to a voltage input is often called a Voltage Controlled Voltage Source or VCVS.A voltage source connected to the current input is also called the Current Controlled Voltage Source or CCVS.

Ideal dependent sources are widely used in the analysis of input/output properties or gain of circuit elements such as transactional amplifiers, transistors and integrated circuits.In general, an ideal voltage-dependent source with voltage or current control is indicated by a diamond-shaped symbol, as shown.

Dependent Voltage Source Symbols

Voltage Source

An ideal dependent voltage controlled voltage source, VCVS equates the output voltage to a multiplication constant (basically an amplification factor) of the control voltage located elsewhere in the circuit.Since the impact constant is a constant, the control voltage V IN will determine the size of the output voltage V OUT. In other words, the output voltage "depends" on the value of the input voltage, which makes it a dependent source of voltage, and in many ways an ideal transformer can be considered a VCVS device with a magnification factor rotation rate.

Then the VCVS output voltage is determined by the following equation: V OUT = μV IN .Note that the multiplication constant is μ sizeless, since μ = V OUT /V IN , therefore its units will be volts/volts.

An ideal dependent current controlled voltage source, CCVS maintains an output voltage equal to some multiplication constant (rho) times of a control current input produced elsewhere in the connected circuit.Then the output voltage "depends" on the value of the input current, which again makes it a dependent voltage source.

As a control current, I IN determines the size of the output voltage, V OUT multiplication constant ε (rho), which allows us to model a current-controlled voltage source as a trans-resistance amplifier as a multiplication constant, gives us the following equation : V OUT = εI IN .This multiplication constant ε (rho) has Ohm units because ε = V OUTPUT /I IS IN and therefore its units will be volts/amps.

Voltage Source Summarize

Here we found that a Voltage Source can be an ideal independent voltage source or a controlled dependent voltage source.Independent voltage sources provide a constant voltage that is not connected to any other amount in the circuit.Ideal independent sources can be AC voltage sources that change over time from batteries, DC generators or alternators.

Independent voltage sources can be modeled as an ideal or practical voltage source for all load currents, such as an ideal voltage source (R S = 0) where the output is constant, or a resistant battery serially connected by circuit.To represent the internal resistance of the source.Ideal voltage sources can only be connected in parallel if they are of the same voltage value.Serial helper or serial opposite connections affect the output value.

In addition, voltage sources for circuit analysis and solving complex theorems become short-circuit sources that equalize their voltage to zero to help solve the network.Also note that voltage sources are capable of both transmitting and absorbing power.

The ideal dependent voltage sources, represented by a diamond-shaped symbol, are connected to an external control voltage or current and are proportional.For a VCVS, there is no multiplication constant, there are no μ units, and the multiplication constant for a CCVS has Ohm units.A dependent voltage source for modeling electronic devices or active devices such as lucrative transactional amplifiers and transistors is of great interest.

In the next lesson on electrical sources, we will look at the compliment of the voltage source, which is the current source, and we will see that current sources can also be classified as dependent or independent sources of electricity.