What is the Current Source

What is the Current Source

• The Current Source is an active component of the circuitry that provides the constant current in a circuit irrespective of the variation in the voltage of the circuitry.
• From the definition of the current source, we can conclude that it is the ideal source. But, in real-world, there are no ideal sources exits.
• For example, it can explain that if we connect an ideal source with open circuitry it will not work.

• There are two main factors that described the working of the practical current source. First is its inner resistance and other is compliance voltage.
• The maximum voltage that the current source can deliver to the load is called compliance voltage.
• During the variation in the load the current source work like ideal source, provides the unlimited resistance but, when the voltage value at the output reaches to compliance voltage, then it starts to behave like a real source and provides the limited value of resistance.

  

Ideal Current Source

• The current source that has unlimited resistance and delivers the same value of the current to load.
• Similar to the voltage source the ideal current sources has two types of dependent and independent current sources.
• The independent sources are such devices that used to resolve such circuitries that have active components like transistors, diodes, etc.
• The simple example of the current source is the resistance that is connected with the voltage source to produce a small value of the current from a few mA to hundred ampers.

  

Connections of the Current Source

• The current sources can be joined with one another to increment and decrement in the value of the current.
• There are two methods by that they are connected with each other according to the circuitry demand. First one is a series and the other is parallel.
• Let's discuss these two connections methods one by one.

• You can see in the given diagram that the 2 current sources are connected parallel. Parallel connected current sources behave like a single source and its output is the sum of the currents of 2 sources.

• In given circuitry, there are 2 five ampers current sources are connected in parallel the output current will be the sum of these two sources current that is ten amperes.
• The sources that have different values can also connect parallel, like if we connect 10-amper and 8-ampere sources in parallel there output will be 18 amperes.

  

• Now we study what will be the effect if we connect the source in the opposite direction.
• In given circuitry two 10 amperes current sources are connected in parallel. The method to get the output of such circuitry is to subtract the value of the 2 current sources, in the given diagram the first circuitry will have zero current.
• In 2nd circuitry there is two parallel-connected circuitry that has 10 amperes and 5-ampere current value, their output will be 5 amperes.

  

• Now we discuss the behaviour of the series-connected current sources.
• It is not good to connect current sources in a series.
• The reason is that the series-connected sources output current do not follow the addition and subtraction rule.
• In given circuitry, there are 2 ten amperes current source are connected in series their output can not be 20 amperes in series combination.

  

Practical Current Source

• As we have discussed above that the ideal current source provides the constant current irrespective of the variation in the output load. Due to this fact it also is known as the independent source.
• So we can say that the ideal current source has unlimited value of the resistance.

• Theoretically, an ideal source is exiting but practically the current source have larger value resistance but not infinity like the ideal source.
• The practical current sink can be constructed like an ideal source if it is linked with the inner resistance in parallel.
• In given circuitry, the resistance (R1) produce the same effect that the resistance connected in parallel with ideal source do.
• As these two circuitries are equivalent so the voltage drop value will also similar.

  

• You can see from the diagram that circuitry of the real source looks like an equivalent circuitry of the Norton, Norton says that any circuitry can be substituted with such circuitry that has one resistance and parallel source with it.
• If the value of the resistance (R1) is higher or unlimited then practical source looks like an ideal source.

Comparison between Current and Voltage Sources

• Mostly electric power source like battery and electric supply in our homes are known as the voltage source.
• All of these sources deliver the same value of the voltage, as the current passing through the circuitry within limits.
• In case of open circuitry, ideal source delivers 0 power but when it is short-circuited it has unlimited power.
• An ideal source has 0 value of resistance when it connected in series circuitry.
• The practical source has some value of resistance but not zero, almost less than one O.
• Try to avoid the use of the ideal sink in the short-circuited arrangments, and not connect it with such source whose voltage value is not similar to the ideal source.

• Current source delivers the same value of the current, till that point the resistance of the load is very less.
• In the case of the short-circuited conditions, the ideal current delivers 0 power but in case of the open circuitry, it gives the unlimited value of power and voltage.
•  Contrary to the ideal sink the practical current sink has the higher but the limited value of the resistance.
• Like voltage source try to avoid the use of the ideal current sink in open-circuited arrangements and with a source that does not have similar current to the ideal source. But sometimes such arrangments used for complementary metal oxides semiconductor circuitries.