# Current Source and Dependent Current Sources

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10 Common Questions You May Find When You’re Discussing about Current Source

Whether you are researchers, experts, lecturers, technicians or even college students who especially learn physics or electrical engineering, you will find the concept of current source in your study. Before we may deal with any DC circuit theory in later study, it’s essential to know what a current source is.

## 1. Let’s Begin with the Simplest Way to Define “Current Source”

What things come up to your mind if you hear the term of current source? The first thing you will do to understand it is divided this term into two words which are ‘current’ and ‘source’. When you hear the word source especially in electronics, you will interpret this term as ‘providing’ something.

The meaning of providing something in this case will appropriately conform to a current. In any case, the meaning of sourcing utterly opposes of sinking which means ‘taking’ or also ‘demanding’ something. However, that will be easiest way to understand current source before going to understanding deeper.

## 2. How Does Exactly Current Source Occur?

A current source itself can be explained as the element of the circuit which can hold a constant current flow negligent of the voltage. The voltage is commonly developed across the terminals and determined by other circuit elements.

According to Franco S., “the current source, which is mostly used in bio-impedance measuring the systems, is the Enhanced Howland circuit due to its simple structure and good performance”.

To be specific, an ideal current source supplies a specified amount of current continually, without reference to the driving impedance. Further, theoretically an ideal current source can provide an infinite amount of energy.

## 3. It’s Essential to Understand Electrical Sources at First

Before understanding the current source, it’s essential to know that there are two types of active circuit elements that supply electrical energy to the circuits called “electrical sources”. The electrical sources itself can be categorized into two types which are the voltage source and the current source.

A source or simply known as an electrical supply is a device that provides electrical power to a circuit. Compared to voltage source, the current source is generally less common in circuits. But still, both voltage source and current source are applied as complements of each other.

Whether it comes to the form of a voltage source or current source, both electrical source types are classed as a (DC) or alternating (AC) source. The DC voltage occasionally can be explained as a constant voltage meanwhile the AC voltage sometimes caries with time.

## 4. An Ideal Current Source and How It Works Exactly

After understanding the concept of current source, now let’s move to the explanation of the ideal current source itself. An ideal current source can also be called a constant current source as it supplies a constant steady state current independent of the load.

Current source can either be independent and dependent current source which depends on the voltage or current in the circuit. Furthermore, it can also be constant or time-varying. An ideal independent current source is occasionally applied to solve circuit theorems that contain real active elements.

If you’re looking for the simplest form of a current source, you may use a resistor in series. It can be designed with a voltage source that creating currents ranging from a few milli-amperes to hundreds of amperes.

## 5. Applying Current Source to Measure DC Resistance of a Wire

Down below are some examples of the utilization of current source:

• Driving LEDs: LEDs occasionally change the level of brightness based on the current flowing. LEDs get the brightness by choosing a resistor value so the temperature will change the device. It will make the forward voltage drop of the diode and make an inconstant value of the resistance.
• Battery Charging: Battery charging also uses an application of current source. It’s occasionally used by the battery technologies which using a Lithium. It requires constant current charging up to a specified voltage level. A current source moreover also lets you control the current value.
• Measuring Resistance: Current source can be used to measure resistance. To apply this, you have to understand the value of the current that flows and the potential difference (voltage) of the resistor. This process needs to be applied in order to determine the value and make it easy to calculate.

## 6. What a Dependent Current Source and How Does it Work?

A dependent current source generally changes an available current. It depends upon the voltage or the current across some other element that connected to the circuit. Put another way, another voltage or current may take a control to the output of a dependent current source.

Dependent current source also has the same action to the current sources whether it comes to ideal/independent or practical. The difference may come to the condition that an input voltage or current controlling a dependent current source.

A current source which is depending on voltage is referred to as a Voltage Controlled Current Source. Meanwhile, a current source that is depending on a current input is commonly referred to as a Current Controlled Current Source.

## 7. Difference between current sources and voltage sources

In a simple way, a current source can be described as two terminal elements provide the flow of current that can be indicated by looking into the direction of the arrow. Further, a current source and voltage source has a relation which is its variables are given by Ohm’s law as these will have specified value

In other hand, with an electrical circuit allows current to flow around, a voltage source which commonly found in a battery and generator supplies a potential difference between two points. Voltage source however can also exist without current due to battery application.

In addition, with the voltage appearance across the positive and negative terminals of the source with the term of ‘terminal voltage’, a battery has been the most general voltage source for circuit. Occasionally, a voltage divider is used to create different levels of voltage from a common voltage source.

## 8. Independent Voltage and Dependent Voltage Sources

Due to four terminals exist, the dependent voltage or voltage controlled current source is the source that the output voltage or current is not fixed. Instead, it depends on the voltage or current that can be found in another part of the circuit.

A dependent source itself will occur when the strength of voltage changes in the source. It’s generally founded in any change of the connected network. A dependent voltage supplies the magnitude that works depend on the voltage across or the current that flows through any other circuit element.

Not same as a dependent voltage, independent sources are not depending on any other quantity in the circuit. There are two terminal devices that each has its own constant value. Further, there remains a constant irrespective of all circuit conditions due to the voltage that across the two terminals.

## 9. An Ideal Voltage Source

An ideal voltage source can be explained as a two terminal active element. It’s able to both supply and maintain the same voltage across the terminals in spite of the current that flows through it. Put another way, an ideal voltage source is able to supply a constant voltage at all times.

An ideal voltage source is ordinarily known as an independent voltage source. It’s because the voltage doesn’t depend on the value of the current that flows through the source, or its direction. Instead, it is determined by the value of the source itself.

## 10. How to Connect a Voltage Sources Together?

When it comes to the connecting a voltage sources together, there will be two kinds of way that are parallel and series. Both parallel and series can be applied for any circuit element due to the same value each has. Exception, only the unequal ideal voltage sources can’t be directly connected in parallel.

### Voltage Source in Parallel

As long as they have the same voltage value, ideal voltage sources can be connected in parallel although it may not be the best practice for any circuit analysis. But remember, it may not be allowed to connecting ideal voltage sources with different voltage values or short-circuited by an external branch together.

### Voltage Source in Series

Voltage sources can also be connected by applying series with connecting every polarity. It will make the plus terminal of one connected to the negative terminal of the next. It also allows current to flow in the same direction as well.

## 11. Inversion of the Current Source

The current source inverter once in a while is used to convert the input direct current to become an alternating current. The current source inverter sometimes is also known as a current fed inverter. Especially in current source inverter, the input currents may remain constant but it still can be adaptable.

Basically, the inverter has an output voltage which is independent of the load. Furthermore, when it comes to a magnitude and nature of the load current, it should be depended on the nature of load impedance. Read also current divider.   