Dependent Sources

Definition: What are Dependent Sources?

Types of Dependent Sources: Dependent Voltage Source and Dependent Current Source

Put simply, dependent sources fall into two critical categories. These are the Dependent Voltage Source (DVS) and Dependent Current Source (DCS).

• A dependent voltage source (DVS) is a voltage source whose supplied voltage varies depending on the current or voltage of another part of the circuit.
• A dependent current source (DCS) is a current source whose current changes according to the current or voltage elsewhere in the circuit.

Use cases: Dependent Source Circuit Creation

Now that you understand the basics of dependent sources, how are they actually applied? Well, dependent sources prove to be indispensable in several technical applications and analyses.

Overall, dependent sources are the building blocks for various gadget and circuit designs that need adaptable and flexible operating conditions.

Examining Thevenin Equivalent with Dependent Sources

Thevenin’s theorem is a critical method used in electronics and electrical engineering to simplify complex circuits. When circuits contain dependent sources, the theorem presents a helpful way to simplify circuit analysis considerably.

Basics of Thevenin Theorem

Thevenin's Theorem is a technique in electrical engineering that simplifies the examination of complex circuits. Essentially, it postulates that any linear bilateral network, regardless of its complexity or the number and type of components it comprises, can be represented by an equivalent circuit consisting of a single voltage source (Thevenin voltage \( V_{Th} \)), and a series resistance (Thevenin resistance \( R_{Th} \)).

It's worth mentioning that the theorem is especially valuable in the context of electrical networks with a changing load. In the context of dependent sources, the theorem's utility becomes evident as it fundamentally simplifies the task of circuit analysis.

Application of Thevenin Equivalent in Dependent Source Circuits

When applying Thevenin’s Theorem to circuits that include dependent sources, there are a few specific steps needed to accurately determine the Thevenin equivalent circuit.

1. Locate the Load: Identify the load resistor for which you want to find the Thevenin equivalent circuit. This will be where your simplified Thevenin circuit will output to.
2. Determine \( V_{Th} \): Nullify all independent sources(switch off all independents voltage sources and short all independent current sources) and figure out the remaining voltage at the output terminals 'a-b'. This is your \( V_{Th} \).
3. Calculate \( R_{Th} \): Create a test source on the output terminals 'a-b'. Observe the response of the circuit to this test source. The \( R_{Th} \) can be calculated using the determined test source voltage or current and the response using Ohm's law.
4. Construction of the Thevenin equivalent circuit: A dependent Thevenin equivalent circuit is constituted with \( V_{Th} \) and \( R_{Th} \) discoveries.

By taking the time to master Thevenin’s theorem, you'll have a helpful tool in your physics toolkit for simplifying and analysing circuits that incorporate dependent sources. It adds much-needed simplicity to the world of electronic circuit analysis.

Analysis Techniques with Dependent Sources

Analysing circuits with dependent sources can be a bit more complex than those with only independent sources. Several techniques are used to simplify the process. These include the Superposition Theorem, Mesh Analysis, and Nodal Analysis. These methodologies disentangle complex circuit problems, streamlining the analysis and making problem-solving a more efficient exercise.

Superposition Theorem with Dependent Sources

The Superposition Theorem is a strategy that tech enthusiasts often employ when they encounter circuits with multiple sources. The theorem states that in a linear system, the net response at a given place and time caused by two or more stimuli, is the sum of the response which would have been caused by each stimulus individually, without the presence of the others. Hence, the total response of the system is the "superposition" of responses from individual stimuli.

For you to use the Superposition Theorem with dependent sources, it's necessary that the controlling quantity isn't nullified. This arises because dependent sources introduce an added layer of complexity due to their reliance on circuit parameters. The connection to the controlling source should be retained.

• Step 1: Consider one source at a time while all others are deactivated.
• Step 2: Determine each current and voltage for the chosen source.
• Step 3: Add up the currents and voltages separately to get the total.

It's crucial to note that if dependent sources are controlled by the values of the independent sources, it's not possible to independently set the controlling source's value to zero. When you use superposition with dependent sources, it's beneficial to draw separate diagrams for each source whilst noting the impact of other sources on the circuit to prevent errors.

Using Mesh Analysis with Dependent Current Source

Mesh Analysis, also known as Loop Current Method, is a technique used for solving circuits to obtain loop currents and potentials in a network. A loop or mesh in this context refers to a closed conducting path. This method significantly simplifies the process of analysing complex circuits, particularly solvable by the Kirchhoff's Voltage Law (KVL).

For a dependent current source within a mesh, it's a little more complex. The concept of a "supermesh" is introduced. A supermesh forms when a dependent current source touches two meshes. Here, you treat the two meshes the dependent source touch as one and apply KVL over this supermesh excluding the dependent current source.

Mesh analysis with dependent current sources can be conveniently broken down into several steps:

1. Determine and label each of the meshes in the circuit. When a dependent source is present, the meshes touching it form a supermesh.
2. Set up the KVL equation for each regular mesh and the supermesh.
3. Solve the generated simultaneous equations to find the mesh currents.

Nodal Analysis with Dependent Voltage Source

Nodal Analysis is another potent technique used when dealing with circuits. This method works by focusing on the nodes of a circuit to ascertain the voltage at each node. It can be particularly helpful when analyzing circuits with dependent voltage sources.

However, when it comes to dependent voltage sources, it introduces a bit of a challenge in nodal analysis. This is because a dependent voltage source doesn’t set the voltage between the two nodes to a specific value. Instead, its value relies on a specific condition. Therefore, one of the nodes in the circuit has an unknown voltage, creating an additional unknown in the analysis.

To solve this issue and simplify the network, an 'auxiliary' node is introduced in the circuit. This breaks the dependent voltage source into two nodes - ensuring the voltage at each node in a circuit is known. Now, the nodes in connection with a dependent voltage source don't affect the node equations, and nodal analysis can be applied smoothly.

Benefits of Nodal Analysis for Dependent Voltage Sources

Nodal Analysis provides a methodical way of determining every voltage within a reciprocal linear DC network. By focusing on node voltages (rather than currents) as the main unknowns, the process promotes ease when dealing with dependent voltage sources.

Firstly, nodal analysis reduces the number of equations you'll need to solve at once. This makes it ideal for computer-based calculations where large circuit networks pose a computational issue.

Secondly, it works efficiently with circuits having several components connected in parallel. Nodal analysis gives direct access to the voltage across every parallel element, which is often the main parameter of interest.

Thirdly, it also suits circuits where multiple inputs affect the node voltage. When dealing with a dependent voltage source, these benefits translate into a cleaner, less complicated analysis approach.

Steps to Perform Mesh Analysis with Dependent Current Source

When performing Mesh Analysis with a Dependent Current Source, you must follow specific steps to get accurate results. Here's your guide to make it simpler:

1. Identify and label each of the loops in the circuit. If a dependent current source is present, treat the loops it touches as a supermesh - a theoretical larger loop.
2. Write the Kirchhoff’s Voltage Law equation for each standard loop and the supermesh as well, eliminating the dependent source.
3. Supplement these equations with other provided by the nature of the dependent sources.
4. Solve the system of equations which gives the loop’s current.
5. Determine the circuit quantities of interest.

Boldly following these steps, you'll soon find the precise and efficient nature of Mesh Analysis in circuits with dependent current sources.