Step 1
Control Signal Defined
A small voltage or current elsewhere in the circuit is identified as the controlling variable.
Circuit Element Explanation
Dependent Source
A dependent source is an ideal controlled source whose output voltage or current depends on another voltage or current elsewhere in the circuit.
Back to Circuit ElementsExplanation
- It is a circuit element whose value is controlled by a separate circuit variable, not by its own terminals alone.
- Dependent sources model transistors, op-amps, amplifiers, and other active devices.
- The control signal sets the output relation, while the actual output power comes from an external supply.
Formula
VCVS: Vout = A Vin
- This is one ideal example: a voltage-controlled voltage source.
- Vout is the output voltage produced by the dependent source.
- Vin is the controlling input voltage measured in a different part of the circuit.
- A is the gain factor; it defines the relationship, not the energy source.
- There are four dependent source types: VCVS, VCCS, CCVS, and CCCS.
Key Idea
A dependent source is controlled by another circuit variable and relies on external power to deliver output energy.
Visual Explanation Steps
Show a VCVS model where Vin controls the output voltage relation and the amplifier power rails supply the actual energy.
Step 2
Control Relation Only
The dashed line shows a mathematical control relation. It is not a physical path for output power.
Step 3
Output Follows The Control
The dependent source sets its output voltage or current based on the input control signal and gain factor.
Step 4
External Supply Delivers Energy
The source itself does not create energy. The extra output power comes from an external power supply.