Current-Controlled Voltage Source

A current-controlled voltage source is a dependent source that produces an output voltage proportional to a current elsewhere in the circuit. In Intro to Electrical Engineering, you use it when analyzing circuits with feedback or source-dependency.

What is Current-Controlled Voltage Source?

A current-controlled voltage source is a dependent source in Intro to Electrical Engineering, meaning its voltage output is set by a current somewhere else in the circuit. If the controlling current changes, the source voltage changes too. The relationship is usually written as v = r_m i_x, where i_x is the controlling current and r_m is the proportionality constant in ohms.

That makes it different from an independent battery or ideal source. An independent source holds its value no matter what the circuit is doing, but a dependent source responds to another circuit variable. In a schematic, this source is often drawn as a diamond shape to show that it is controlled rather than fixed.

A current-controlled voltage source is useful for modeling devices and amplifier behavior, especially when the output depends on current flowing through another part of the network. You may see it in simplified circuit models for transistors or feedback systems, where one part of the circuit senses current and another part produces a matching voltage response.

When you analyze one, the main job is to keep track of the controlling current and the output voltage separately. The controlling current might be the current through a resistor, a branch, or a labeled element in the circuit. Once you identify that current, you can plug it into the source equation and relate it to the rest of the circuit using Ohm's Law, KVL, or KCL.

This is also where superposition can get tricky. You can turn off independent sources one at a time, but dependent sources stay active because they are part of the circuit model. So if a current-controlled voltage source is in the circuit, you do not erase it during circuit decomposition. Instead, you keep its control relationship and solve for the controlling current from the reduced circuit.

A quick example helps. Suppose a dependent source is labeled v = 4i_x, and the controlling current i_x is 2 mA. The source voltage is 8 mV. If another part of the circuit changes i_x to 5 mA, the source voltage becomes 20 mV. The source is not choosing a voltage on its own, it is translating current into voltage according to the circuit's rule.

Why Current-Controlled Voltage Source matters in Intro to Electrical Engineering

Current-controlled voltage sources show up whenever a circuit element's output depends on another current, which is a standard idea in circuit modeling. That makes them a big part of linear circuit analysis, especially when you are building equivalent models for amplifiers, feedback loops, or controlled devices.

This term also connects directly to the algebra of solving circuits. You cannot treat it like a standalone battery. You have to identify the controlling current, write the dependent-source equation, and combine that with Ohm's Law and the circuit laws to solve for unknown voltages and currents. That is the same reasoning you use in problem sets with nodal or mesh analysis.

It matters even more in superposition problems. Independent sources get turned off one at a time, but the dependent source stays in place, which means you still have to track how the rest of the circuit affects it. That is a common place to make mistakes, so knowing how the source behaves helps you avoid wiping out the very part of the circuit you need.

This concept also builds intuition for real devices. In a lab or homework model, you may not be working with the exact physical component, but the dependent source captures the input-output relationship well enough to predict circuit behavior. That makes it a useful bridge between ideal circuit diagrams and actual electronics.

How Current-Controlled Voltage Source connects across the course

Dependent Source

A current-controlled voltage source is one specific kind of dependent source. The broader category includes any source whose value depends on another voltage or current in the circuit. If you recognize the source as dependent, you know it stays active during analysis and needs its control variable tracked carefully.

Superposition Theorem

Superposition is where this source often shows up in homework problems. You can deactivate independent sources one at a time, but you cannot turn off the dependent source because its value is tied to circuit variables. That means the controlling current still has to be found from each reduced circuit.

Ohm's Law

Ohm's Law is usually the next step after identifying the controlling current. If that current flows through a resistor, you may use v = iR to rewrite the control variable in terms of voltages or branch currents. That turns the dependent source into something you can solve inside the circuit equations.

Voltage-Controlled Voltage Source

This is the close cousin people mix up with a current-controlled voltage source. Both are dependent voltage sources, but the controlling variable is different. One responds to a current, while the other responds to a voltage, so the setup and the algebra change depending on which symbol appears in the circuit.

Is Current-Controlled Voltage Source on the Intro to Electrical Engineering exam?

A quiz or problem set question will usually give you a circuit diagram with a diamond-shaped source and ask for the output voltage, branch current, or controlling variable. Your job is to identify what current controls the source, write the dependent-source equation, and combine it with KCL, KVL, or Ohm's Law to solve the circuit. In a superposition problem, leave the dependent source active while you turn off the independent sources. If the source is part of a feedback-style circuit, expect to trace how one branch current changes the rest of the network instead of treating the source as fixed.

Current-Controlled Voltage Source vs Voltage-Controlled Voltage Source

These sound almost the same, but the control variable is different. A current-controlled voltage source uses a current to set the output voltage, while a voltage-controlled voltage source uses a voltage to set the output voltage. In circuit problems, that means you have to look closely at the label on the diamond source before you write the source equation.

Key things to remember about Current-Controlled Voltage Source

• A current-controlled voltage source is a dependent source whose output voltage depends on a current elsewhere in the circuit.

• The controlling current and the source voltage are linked by an equation, often written in the form v = r_m i_x.

• You do not turn off dependent sources during superposition, because their value comes from the circuit itself.

• The diamond symbol tells you the source is controlled, not independent.

• These sources are common in circuit models for amplifiers, feedback systems, and other linear network problems.

Frequently asked questions about Current-Controlled Voltage Source

What is a current-controlled voltage source in Intro to Electrical Engineering?

It is a dependent voltage source whose output depends on a current elsewhere in the circuit. The circuit diagram usually shows it as a diamond, and the label tells you which current controls it. You solve it by finding that current and plugging it into the source equation.

How do you know if a source is current-controlled or voltage-controlled?

Look at the control label on the diamond source. If the output voltage is written in terms of a current, it is current-controlled. If it is written in terms of a voltage, it is voltage-controlled. That small label changes the whole setup of the problem.

Do you turn off a current-controlled voltage source in superposition?

No. You turn off only independent sources in superposition. A current-controlled voltage source stays active because it depends on a circuit variable, so removing it would change the circuit you are trying to analyze.

How do you solve a circuit with a current-controlled voltage source?

First identify the controlling current, then write the dependent-source equation. After that, use KCL, KVL, and Ohm's Law to connect the source to the rest of the circuit. The main challenge is keeping the control variable visible while you simplify the network.