![](http://engredu.com/wp-content/uploads/2022/05/LTSpice_Icon.png)
LTSpice Dependent Sources
Introduction
An ideal dependent (or controlled) source is an active element in which the source quantity is controlled by another voltage or current.
There are 4 different types of dependent sources:
- VCVS - Voltage Control Voltage Source
- CCVS - Current Control Voltage Source
- VCCS - Voltage Control Current Source
- CCCS - Current Control Current Source
Let's learn this by example.
VCVS
The schematic symbol for a voltage control voltage source is the following:
![](http://engredu.com/wp-content/uploads/2022/05/image-42.png)
In LTspice the "e" component represents a VCVS.
![](http://engredu.com/wp-content/uploads/2022/05/image-45.png)
Circuit example:
![](http://engredu.com/wp-content/uploads/2022/05/image-43.png)
To make the schematic easier to read, we use labels instead of wires to connect the VC terminals of "e" to the desired nodes.
Note: Be aware if you place the ground reference at a different node, you will get different results for the voltage at the other nodes. Currents will be the same independently where you place the ground reference.
![](http://engredu.com/wp-content/uploads/2022/05/image-44.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-46.png)
VCCS
The schematic symbol for a voltage control current source is the following:
![](http://engredu.com/wp-content/uploads/2022/05/image-50.png)
In LTspice the "g" component represents a VCCS.
![](http://engredu.com/wp-content/uploads/2022/05/image-51.png)
Circuit example:
![](http://engredu.com/wp-content/uploads/2022/05/image-52.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-54.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-53.png)
CCVS
The schematic symbol for a current control voltage source is the following:
![](http://engredu.com/wp-content/uploads/2022/05/image-47.png)
In LTspice the "h" component represents a CCVS.
Note: The "h" component requires a current through a voltage source. If the controlled current of your circuit doesn't come from a voltage source, there are ways to work around this. Check Example 2 under Other Examples to see how to address that issue for a CCVS.
![](http://engredu.com/wp-content/uploads/2022/05/image-49.png)
Circuit example:
![](http://engredu.com/wp-content/uploads/2022/05/image-48.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-61.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-60.png)
CCCS
The schematic symbol for a current control current source is the following:
![](http://engredu.com/wp-content/uploads/2022/05/image-55.png)
In LTspice the "f" component represents a CCCS.
Note: The "f" component requires a current through a voltage source. If the controlled current of your circuit doesn't come from a voltage source, there are ways to work around this. Check Example 1 under Other Examples to see how to address that issue for a CCCS.
![](http://engredu.com/wp-content/uploads/2022/05/image-56.png)
Circuit example:
![](http://engredu.com/wp-content/uploads/2022/05/image-58.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-57.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-59.png)
Other Examples
Example 1
![](http://engredu.com/wp-content/uploads/2022/05/image-62.png)
For CCCS dependent sources in LTSpice the "f" component requires a controlled current through a voltage source. For this particular example, the controlled current is related to a resistor. There are a couple of ways to simulate this situation.
Option 1
Include a voltage source of 0V on the branch where the controlled current is present. The direction of this voltage source should have the controlled current entering the negative side of it.
![](http://engredu.com/wp-content/uploads/2022/05/image-70-1024x606.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-71.png)
Option 2
You can also use the arbitrary behavioral current source "bi".
![](http://engredu.com/wp-content/uploads/2022/05/image-66.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-64.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-67.png)
Example 2
![](http://engredu.com/wp-content/uploads/2022/05/image-63.png)
For CCVS dependent sources in LTSpice the "h" component requires a controlled current through a voltage source. For this particular example, the controlled current is related to a resistor. There are a couple of ways to simulate this situation.
Option 1
Include a voltage source of 0V on the branch where the controlled current is present. The direction of this voltage source should have the controlled current entering the negative side of it.
![](http://engredu.com/wp-content/uploads/2022/05/image-72.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-73.png)
Option 2
You can also use the arbitrary behavioral voltage source "bv".
![](http://engredu.com/wp-content/uploads/2022/05/image-65.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-69.png)
![](http://engredu.com/wp-content/uploads/2022/05/image-68.png)
LTSpice Simulation Files
References
- [Ref 1] "LTspice tutorial - Ep7 Dependent voltage and current sources", FesZ Electronics YouTube Channel [Video]