VCC, VDD, VEE, VSS and GND: Meaning of the power supply voltage abbreviations

In the field of electronic engineering, power supply voltage is an integral part of circuit design. To simplify the annotation of circuit diagrams and improve work efficiency, engineers often use some abbreviations to represent different power supply voltages. This article will introduce these common power supply voltage abbreviations in detail: VCC, VDD, VEE, VSS and GND.

What are VCC, VDD, VEE, VSS and GND?

VCC: Positive Supply Voltage for TTL and CMOS Logic
VCC, the full name of "Collector supply voltage", was originally designed for transistor-transistor logic (TTL) circuits and refers to the supply voltage of the collector of the transistor. However, over time, the meaning of VCC has gradually become generalized and has become a universal mark for almost all positive power supply voltages, especially in complementary metal oxide semiconductor (CMOS) logic circuits. VCC usually represents the highest positive supply voltage in the circuit and provides the necessary working energy for digital logic circuits.

VDD: Drain Supply Voltage in MOSFETs
VDD, or "Drain supply voltage", refers to the supply voltage of the drain in MOSFET (metal oxide semiconductor field effect transistor) circuits. Similar to VCC, VDD is also often used as a positive power supply voltage identifier, especially in modern integrated circuit design. Whether in digital logic or mixed signal circuits, VDD is the most common power supply voltage symbol. The value of VDD directly determines the maximum operating voltage range of the circuit.

VEE: Negative Supply Voltage
VEE, which stands for "Emitter supply voltage" in early transistor circuits, but later evolved to refer to negative power supply voltage. In many analog circuits and bipolar power supply systems, VEE identifies the lowest negative power supply voltage, corresponding to VCC or VDD, providing a negative bias voltage for the circuit to ensure stable operation of the circuit and correct signal processing.

VSS: Signal Ground or Second Supply Voltage
VSS, the abbreviation of "Signal ground" or "Second supply voltage", mainly appears in dual power supply circuits. In most cases, VSS is synonymous with GND (Ground), representing the signal ground or reference point in the circuit. But in some circuit designs, especially those that require positive and negative dual power supplies, VSS can refer to a second power supply voltage different from GND, usually a negative voltage, to provide power for the negative voltage part of the circuit.

GND: Ground Reference
GND, the full name of "Ground", is the most basic and important reference point in the circuit, representing the zero potential point in the circuit. GND is not only the reference for all voltage measurements in the circuit, but also an essential part of the current loop. In circuit design, it is crucial to ensure the stability of GND because it directly affects the integrity of the signal, the efficiency of the power supply, and the performance and reliability of the entire system.

Definitions of VCC, VDD, VEE, VSS, and GND

• VCC: C=circuit means circuit, that is, the voltage connected to the circuit.

• VDD: D=device means device, that is, the internal operating voltage of the device.

• VEE: negative voltage power supply; source of field effect transistor (S)

• VSS: S=series means common connection, usually refers to the common ground voltage of the circuit.

• GND: usually defined as the voltage reference point in the circuit.

What is the difference between VCC main and VDD main?

VCC (Vin Collector): Commonly used in transistor circuits, especially NPN transistors. When VCC is mentioned, it generally refers to the collector supply voltage of the transistor. In these circuits, the collector of the transistor is connected to this supply, while the emitter is grounded or connected to a lower potential. VCC is usually the highest voltage reference point of the circuit.

VDD (Vin Drain): Mainly used in MOSFET (Metal Oxide Semiconductor Field Effect Transistor) circuits, especially in NMOS and CMOS technology. VDD stands for the drain supply voltage because the drain of the MOSFET is connected to this supply. In these circuits, the source of the MOSFET is usually grounded or connected to a lower potential, and the gate controls the current flow from the drain to the source.

What is the difference between GND and VSS?

Although both GND and VSS are related to the reference ground of the circuit, their specific meanings and uses are different:

GND (Ground):

• GND represents the common reference ground of the circuit and is usually considered to be the zero voltage point in the circuit. The ground terminals of all circuits are connected to GND to provide a stable reference potential.

• GND is used not only in analog circuits, but also in digital circuits. It acts as a reference potential in the circuit, and all other voltages are measured relative to GND.

• In power modules, GND usually represents the ground wire of the power supply, which is the negative end of the power supply output.

VSS (Voltage Supply Sink):

• VSS is often used in integrated circuits (ICs), especially in dual-power ICs. VSS represents the negative end of the power supply, which is usually the lowest potential point of the IC.

• In dual-power circuits, VSS is usually connected to the negative pole of the power supply, and VDD is connected to the positive pole of the power supply. In this way, the IC can form a differential voltage between the two power supplies and work normally.

• In some single-power circuits, VSS may also be used as a common reference ground for the circuit, similar to the role of GND.

Summary:

• GND: usually represents the common reference ground of the circuit, which is the ground wire of the power module.

• VSS: usually represents the negative power supply terminal of the integrated circuit, and is connected to the negative pole of the power supply in a dual-power circuit.

Difference Between VCC VDD VEE VSS and GND

• VCC: Positive power supply voltage in bipolar transistor circuits.

• VDD: Positive power supply voltage in field effect transistor and CMOS circuits.

• VEE: Negative power supply voltage in bipolar transistor circuits.

• VSS: Negative power supply voltage or ground voltage in field effect transistor and CMOS circuits.

• GND: Zero voltage reference point in circuits.

Do you know how many types of GND there are?

GND can be divided into several different types according to different applications and circuit types:

Signal Ground:
This is the most common type of ground and is used to provide a reference point for signals in the circuit. All signals are voltage changes relative to the signal ground.

Power Ground:
The power ground is the negative end of the power supply and is usually connected to the negative terminal of the battery or the ground wire of the power adapter. It provides a stable voltage reference for the circuit.

Protective Ground:
Also known as safety ground, it is used to protect equipment and users from the risk of electric shock. It is usually connected to the metal casing of the device to ensure that any leakage current can flow safely into the ground.

Digital Ground:
Used in digital circuits as a reference point for logic levels. Usually connected to the ground pin of the IC.

Analog Ground:
Used in analog circuits as a reference point for analog signals. Usually requires to be cleaner than digital ground to avoid noise interference.

Floating Ground:
Floating ground means that the circuit is not directly connected to the ground, but is isolated from the ground by high impedance. This grounding method is often used in some measuring instruments and isolation circuits to reduce ground loop noise.

Cold Ground:
In AC circuits, cold ground refers to the neutral line (N) of the AC power supply, which is usually connected to the ground but not charged.

Hot Ground:
In AC circuits, hot ground refers to the phase line (L) of the AC power supply, which carries voltage relative to the neutral line (N) and the ground line (PE).

Shield Ground:
Used to shield electromagnetic interference (EMI) and radio frequency interference (RFI). Usually connected to the outer layer of the shielded cable to provide a low impedance path for interference current to flow into the ground.

Summary

Knowing about VCC, VDD, VEE, VSS and GND can help us complete our work more efficiently. These seemingly simple letter combinations actually carry rich technical meanings and functional directions!