Current source method

Current Source method | Current Source | Voltage Source
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2. Current source method Submitted by: Submitted to: Abdul Ahad , 20685 Dr. Fayyaz Ahmad 2

3. CONTENTS Introduction Current Source Voltage source Voltage Source to Current source conversion Current Source to Voltage source conversion References   3

4. source A Source is a device which converts mechanical, chemical, thermal or some other form of energy into electrical energy. In other words, the source is an active network element meant for generating electrical energy. 4

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6. Current Sources A Current Source is an active circuit element that is capable of supplying a constant current flow to a circuit regardless of the voltage developed across its terminals. As its name implies, a current source is a circuit element that maintains a constant current flow regardless of the voltage developed across its terminals as this voltage is determined by other circuit elements. T here are no reliable current sources are available. The current source can be made by putting a very high resistance in series with a voltage source. 6

7. Ideal Current Source An ideal current source may supply infinite amount of energy. Then an ideal current source is called a “constant current source” as it provides a constant steady state current independent of the load connected to it producing an I-V characteristic represented by a straight line. As with voltage sources, the current source can be either independent (ideal) or dependent (controlled) by a voltage or current elsewhere in the circuit, which itself can be constant or time-varying. 7

8. Ideal independent current sources are typically used to solve circuit theorems and for circuit analysis techniques for circuits that containing real active elements. The simplest form of a current source is a resistor in series with a voltage source creating currents ranging from a few milli-amperes to many hundreds of amperes. Remember that a zero-value current source is an open circuit as R = 0. The concept of a current source is that of a two-terminal element that allows the flow of current indicated by the direction of the arrow. Then a current source has a value, i , in units of amperes, (A). The physical relationship between a current source and voltage variables around a network is given by Ohm’s law as these voltage and current variables will have specified values. 8

9. practical Current Source A practical or non-ideal current source can be represented as an ideal source with an internal resistance connected across it. The internal resistance (R P ) produces the same effect as a resistance connected in parallel (shunt) with the current source as shown. Remember that circuit elements in parallel have exactly the same voltage drop across them. 9

10. Parallel adding Current Sources Connecting two or more current sources in parallel is equivalent to one current source whose total current output is given as the algebraic addition of the individual source currents. Here in this example, two 5 amp current sources are combined to produce 10 amps as = +   10

11. Parallel Opposing Current Sources Here, as the two current sources are connected in opposite directions (indicated by their arrows), the two currents subtract from each other as the two provide a closed-loop path for a circulating current complying with Kirchoff’s Current Law, KCL. So for example, if the two currents are of different values, 5A and 3A, then the output will be the subtracted value with the smaller current subtracted from the larger current. Resulting in a of 5 – 3 = 2A. We have seen that ideal current sources can be connected together in parallel to form parallel-adding or parallel-opposing current sources. What is not allowed or is not best practice for circuit analysis, is connecting together ideal current sources in series combinations.   11

12. Ideal Voltage Source A voltage source is a two-terminal device whose voltage at any instant of time is constant and is independent of the current drawn from it. Such a voltage source is called an Ideal Voltage Source and have zero internal resistance. The example of voltage sources is batteries and alternators. Practically an ideal voltage source cannot be obtained. 12

13. Practical Voltage Source Sources having some amount of internal resistances are known as Practical Voltage Source. Due to this internal resistance; voltage drop takes place, and it causes the terminal voltage to reduce. The smaller is the internal resistance (r) of a voltage source, the more closer it is to an Ideal Source. 13

14. Voltage Source to Current source conversion   Assume a voltage source with terminal voltage V and the internal resistance r. This resistance is in series. The current supplied by the source is equal to: when the source of the terminals are shorted. This current is supplied by the equivalent current source and the same resistance r will be connected across the source. The voltage source to current source conversion is shown in the following figure.   14

15. Current Source to Voltage source conversion A ssume a current source with the value I and internal resistance r. Now according to the Ohm’s law, the voltage across the source can be calculated as Hence, voltage appearing, across the source, when terminals are open, is V.   15

16. references https://www.electronics-tutorials.ws/dccircuits/current-source.html https://circuitglobe.com/voltage-source-and-current-source.html https://en.m.wikipedia.org/wiki/Current_source https://www.electrical4u.com/source-of-electrical-energy/ 16

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