What is vdd and vss in electronics?

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.

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…

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).

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.

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

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

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.

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.

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.

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.

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).

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.

This article explains the meaning and differences between VCC, VEE, VDD, and VSS.

The meanings and differences of VCC, VEE, VDD, and VSS used in the supply voltage are shown below.

We will now discuss VCC, VEE, VDD, and VSS in detail in turn.

VCC is used as the positive supply voltage for circuits using a bipolar transistor (BJT).

The positive supply voltage on the collector side of the NPN bipolar transistor is "VCC". The collector terminal of an NPN bipolar transistor is often connected directly to VCC or VCC through a resistor or other means.

The "C" in "VCC" stands for Collector. It is widely believed that the reason for repeating "VCC" and "C" twice is to distinguish it from the collector voltage VC.

Circuits that use multiple positive supply voltages are often represented by different supply voltages, such as "VCC1, VCC2, …".

VCC is also used as the positive supply voltage for operational amplifiers, whose main elements that make up the internal circuit are bipolar transistors, and for TLL (Transistor-transistor logic).

VEE is used as a negative supply voltage for circuits that use a bipolar transistor (BJT).

The negative supply voltage on the emitter side of the NPN bipolar transistor is "VEE". The emitter terminal of an NPN bipolar transistor is often connected directly to VEE or VEE through a resistor or other means. In the case of a single power supply system, "VEE" is at the same potential as the ground.

The "E" in "VEE" stands for Emitter. It is widely believed that the reason for repeating "VEE" and "E" twice is to distinguish it from the emitter voltage VE.

Circuits that use multiple negative supply voltages are often represented by different supply voltages, such as "VEE1, VEE2, …".

VEE is also used as the negative supply voltage for operational amplifiers, whose main elements that make up the internal circuit are bipolar transistors, and for TLL (Transistor-transistor logic).

VDD is used as the positive supply voltage for circuits that use a field-effect transistor (FET).

The positive supply voltage on the drain side of the N-channel field-effect transistor (NchFET) is "VDD". The drain terminal of an N-channel field-effect transistor (NchFET) is often connected directly to VDD or VDD through a resistor or other means.

The "D" in "VDD" stands for Drain. It is widely believed that the reason for repeating "VDD" and "D" twice is to distinguish it from the drain voltage VD.

Circuits that use multiple positive supply voltages are often represented by different supply voltages, such as "VDD1, VDD2, …".

VDD is also used as the positive supply voltage for operational amplifiers, whose main elements that make up the internal circuit are field-effect transistors, and for CMOS(Complementary MOS).

VSS is used as the negative supply voltage for circuits that use a field-effect transistor (FET).

The negative supply voltage on the source side of the N-channel field-effect transistor (NchFET) is "VSS". The source terminal of an N-channel field-effect transistor (NchFET) is often connected directly to VSS or VSS through a resistor or other means. In the case of a single power supply system, "VSS" is at the same potential as the ground.

The "S" in "VSS" stands for Source. It is widely believed that the reason for repeating "VSS" and "S" twice is to distinguish it from the source voltage VS.

Circuits that use multiple negative supply voltages are often represented by different supply voltages, such as "VSS1, VSS2, …".

VSS is also used as the negative supply voltage for operational amplifiers, whose main elements that make up the internal circuit are field-effect transistors, and for CMOS(Complementary MOS).

This article described the following information about "VCC, VEE, VDD, and VSS".

Nowadays it is always used Vdd and Vss to refer to the positive and negative voltage respectively. Vdd is normally was used to be 5V but nowadays is 3.3V or even lower 1.8V or 1.2V. Vss is referred to be zero volts.

First of all, the first letter capital V comes from the standard's paragraphs 1.1.1 and 1.1.2, which define that v and V are quantity symbols describing voltage; in lower case it means instantaneous voltage (1.1.1) and in upper case it means maximum, average or RMS voltage (1.1.2). For your reference:

Paragraph 1.2 starts to define the subscripts for quantity symbols. Subscript letters in upper case mean DC values and lower case mean AC values. Supply voltages are obviously DC voltages, so their letters must be in upper case.

The standard defines 11 suffix (letter)s. These are:

This standard predates the MOS transistor (which was patented in August 1963) and thus doesn't have the letters for Source and Drain. It has since been superseded by a newer standard that defines the letters for Drain and Source, but I don't have that standard available.

The further nuances of the standard, that define further rules on how the symbols are written makes for fascinating reading. It's amazing how all this has become common knowledge that is now quietly accepted and understood even without a normative reference.

Paragraph 1.3 defines how subscripts are written, especially when there is more than one. Please read the words of the standard:

So for example VbE means the RMS value (capital V) of the AC component (lower case b) of the Voltage at the Base of a semiconductor device in reference to the DC value of the Voltage of the semiconductor device's Emitter (upper case E).

In case the said semiconductor's emitter is directly connected to ground, which is certainly understood to be a known reference, then the AC RMS voltage at the base is Vb. The DC or RMS voltage at the base is VB and an instantaneous voltage at the base is vb.

Now for the extra credit: Why VCC instead of VC or VDD instead of VD? I used to think that it's colloquial from "Voltage from Collector to Collector" but obviously it's no surprise that it's also defined in the standard:

So VCCB means the DC supply voltage at the semiconductor device's Collector in reference to the device's Base and VCC means the DC supply voltage at the Collector in reference to ground.

At first instinct it would seem that the reduplication of the subscript would lead to ambiguity, but in fact it doesn't. First of all, the cases that would seem ambiguous are quite rare; reading VCC to mean the voltage from a device's collector to the same device's collector is obsiously zero so there's no point describing it. But what happens if the device has two bases? The standard gives an answer. The voltage from base 1 of a device to base 2 of a device is written VB1-B2. And the voltage from base of device 1 to base of device 2 (pay attention here - this is interesting) is written V1B-2B.