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What Are The Differences Between VDD And VSS? (And Similarities)

What Are The Differences Between VDD And VSS? (And Similarities)

The difference between VDD and VSS is that the first is the positive supply voltage and the second is ground. Both are low voltage, but VSS is set aside for analog use and doesn’t work with digital circuits.

VDD is the voltage applied to a circuit to provide power, whereas VSS is the voltage that drives the injection of electrons from one terminal of a battery into the other terminal, generating current through the circuit. The similarity between both is that they come from the same circuit (FET). 

As you probably know, there are different types of logic gates. FET logic gates come with three terminals: drain, gate, and supply. Let me tell you that VSS (negative supply voltage) is connected to the source, whereas VDD (positive supply voltage) is connected to the drain. 

If you want to see a side-by-side comparison of both, this article is exactly what you might be looking for. So, let’s dive into it… 

What Is VDD?

VDD represents the drain voltage.

In a FET transistor, there are three terminals, including a drain and source. The VDD, or drain, takes the positive supply. VDD supplies power to devices on a positive supply (usually 5V or 3.3V).

What Is VSS?

The S in VSS refers to the source terminal. Along with VDD in the FET transistor, VSS takes zero or ground voltage. Both VSS and VDD refer to one type of logic.

Difference Between VDD and VSS

Difference Between VDD and VSS

Before you learn the differences between the two, here’s a short introduction to the voltage supply. 

Voltage Supply

The voltage supply is the voltage in a circuit.

The voltage supply is needed to power the components of an electronic device, such as a computer. The voltage supply can be either direct current (DC) or alternating current (AC).


VSS supplies power to devices on a negative supply (usually 0V or ground).VDD is the positive voltage in an electric circuit.
It is a DC ground potential.It is an AC voltage that changes direction with each half-cycle of the AC waveform.
VEE is also negative just like VSS.VDD can be used interchangeably with VCC when devices use a 5-voltage supply. 
S in VSS refers to the source. D in VDD refers to drain. 
A Table Comparing VSS and VDD

What Are 480 Volts?

480 volts is the standard voltage used in home wiring. It is used for lighting, appliances, computers, and other electronic devices.

What Is Volt?

A volt (V) is a unit of electric potential equal to the force that would produce an electric charge of 1 coulomb per second in a circuit carrying a current of one ampere.

The SI unit for electric potential is the volt; however, some older units of measure still exist in popular use.

In electronics and telecommunications, a volt (V) represents the potential difference between two points on an electrical circuit. In other words, it is a measure of how much energy is available at two points in an electrical circuit. 

The more positive one point or node is, the greater the voltage will be between that node and its neighbor node. 

Conversely, if one point or node has more negative potential than its neighbor node, then that point has less potential energy than its neighbor node; therefore, there will be less voltage between those nodes than when both nodes have equal potential energy but at different levels of positive or negative voltage, respectively.


What is Voltmeter?

A voltmeter measures volts as well as current—this makes it useful for measuring current in AC circuits without having to figure out how much current each component requires to power itself.

What Is The Difference Between Current And Voltage?

Electrons flow through a circuit in the form of current. Voltage is measured by how much energy is needed to push an electron through a conductor.

Current and voltage are both vectors; they have both magnitude and direction.

Current is the amount of charge that flows through a wire or circuit. The more current, the more charge travels down the wire. If there’s no resistance in the circuit, then the current will be constant.

Voltage is measured in volts (V). It’s a measure of how much energy must be applied to push an electron through a conductor. The bigger the voltage, the more energy is needed to push an electron down a conductor.

Current and voltage can be used together to describe how much work (or energy) is required for electrons to travel from one place to another within an electric field. 

For example, if you have two conductors connected with current flowing through them, then you’ll see that as long as there’s no resistance in between them, we can say that there’s no work going on in this system because there’s no energy being transferred into or out of it (energy = mass x speed).

In Ohm’s Law, voltage equals current times resistance, where V is voltage, I is current, and R is resistance.

How Do Earthing, Grounding, And Neutral Differ?

How do earthing, grounding, and neutral differ?
An image of the Transmission Tower

Earthing, grounding, and neutral are all different ways of describing the same thing: the electrical connection between your home and the power line.

Let’s get to know them one by one.


Earthing is a process that allows electricity to move between your body and the earth. This is what keeps us healthy, as it helps create a complete circuit between our bodies and the earth’s natural electrical field.


Grounding devices are used to create pathways for electrons to flow between your body and the earth’s natural electric field.


A neutral is an imaginary point where all wires meet in an electrical system (generally at each fixture’s socket).

The purpose of neutral grounding is to keep all systems in balance by preventing one side from becoming electrically charged more than another. Its job is to carry the return current. The circuit isn’t complete without this wire. 

Watch this video to learn an in-depth overview of earthing.

What is grounding?


  • The three terminals in a FET MOSFET are the gate, drain, and source.
  • The drain terminal, or VDD, is the positive voltage terminal. 
  • Negative voltages are known as VSS sources. 
  • There are not many similarities between the two terminals except that they come from the same MOSFET. 

Further Reads

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