What is the difference between vcc and vdd

English: Vcc, Vdd, Vss, etc. These notations are used in describing voltages at various common power supply terminals at these points, only a wire lead exists between the point and a power source of a given circuit. Apparently this terminology originated in some way from the terminals of each type of transistor, and their common connections in logic circuits i. The absolute distinctions between these common supply terms has since been blurred by the interchangeable application of TTL and CMOS logic families.

Vcc is positive for bipolar devices, and Vdd is mostly positive for single-stage devices. You can also see Vee and Vss in the circuit diagram, which has the same meaning. Since the mainstream chip structure is silicon NPN, Vcc is usually positive. When selecting a chip, be sure to look at the electrical parameters. Vcc is derived from collector supply voltage, Collector Voltage, generally used for bipolar transistors, PNP tube is negative supply voltage, sometimes labeled as -Vcc, NPN tube is positive voltage.

Vdd is derived from the drain supply voltage, Drain Voltage, used in MOS transistor circuits, generally referred to as the positive supply. Because it is rarely used alone. Vss source supply voltage, referred to as negative supply in CMOS circuits, or zero volts or grounded in single supply. Vee emitter power supply voltage, Emitter Voltage, is generally used for the negative supply voltage of the ECL circuit. Vbb base supply voltage, common-base circuit for bipolar transistors. VCC: power supply voltage bipolar device ; power supply voltage 74 series digital circuit ; voice control carrier Voice Controlled Carrier.

Previous article:. So I would have to say that it's just universally accepted that V CC is the supply voltage of a bipolar circuit and V DD is the supply voltage of a MOS circuit and that is stems from history. If someone could offer a normative reference to the last point discussed, I would be immensely grateful!

Voltage is a potential measured with respect to another point in the circuit. For example V BE is the voltage between base and emitter. Ground does not have a specific "letter". Using single letters in this context adds more confusion since Vs may refer to the voltage of a source "s" which may be different than V SS if there are multiple sources in series, etc. Even without transistors in a circuit, voltages can be referred to with the style V AB or V 12 to reflect potential between A and B or point 1 and point 2.

Bibliographic reference: "If the same letter is repeated, that means a power supply voltage: Vcc is the positive power-supply voltage associated with the collector, and Vee is the negative power-supply voltage associated with the emitter".

Chapter 2 - Transistors, page 62, Introduction. It stands for voltage at drain. It's usually the most positive voltage but not always, for example a motor controller might have a Vs pin for the motor voltage, or a processor might use a core voltage and an IO voltage. Vss stands for voltage at source; PMOS devices might be positive, but again, PMOS is a relic, so for all intents and purposes it is the most negative voltage available.

It's often tied to the substrate, so it must be the most negative, or the chip won't work properly. Vcc stands for voltage at collector and is primarily used for bipolar devices, although I have seen it used with CMOS devices, probably out of convention.

Vee stands for voltage at emitter and is usually the most negative. Suppose want a name for a voltage associated with the collector which is not the voltage at the collector. Suppose we want the name to be as short as possible, but we want to include the letter C to clearly associate it with the collector.

This means that the name will be two symbols long: C plus another character. The other character will be a letter, number or some other kind of glyph.

A number would look like a voltage, so the choice is between using a glyph like ampersand or hash, or a second letter. If the C is repeated, then we know it cannot be the useless designation of the voltage from C to C, which reminds us that the notation has another meaning. There are a small proportion of devices which use multiple supplies relative to ground and in some of these it may make sense to use eg Vee gnd or Vss.

In other cases there may be multiple supplies or grounds which are at the same potential but separated for system reasons. These may be named eg Vccd and Vcca. Similarly you may get Vssa and Vssd. Level translating ICs or ones which MAY be used in that mode such as the CD - see datasheet here Different enough and educational enough to be worth quoting Control of analog signals up to 20VP-P can be achieved by digital signal amplitudes of 4.

In the system that this is used in Vih would probably be termed Vdd or some other name to distinguiosh it from Vcc. There are some gates which allow level conversion the other way. However from my comment below :. The original question was not phrased with logical or analog in mind.

There are numerous applications around using CMOS inverters as linear amplifiers and this is not even an "improper" use of them - just less usual. But, point taken. Actually it's much worse.

In many schematic capture component libraries, supply voltage pins are sometimes hidden in some component symbols. It's not uncommon to download component libraries where some components have a hidden "VCC" or "GND" net connected to the supply voltage pins.

In other components the hidden nets might be called other names. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Asked 10 years, 3 months ago. Active 1 year, 2 months ago.