Introduction:What is the difference between VCC,VDD,VEE and VSS in a circuit?

1. Explanation

  DCpower generally refers to the source with the actual voltage, and the others are labels (in some simulation software, the default label is connected to the source)VDD: power supply voltage (unipolar device); Power supply voltage (4000 series digital circuit); Drain voltage (FET)VCC: power supply voltage (bipolar device); Power supply voltage (74 series digital circuit); VoiceControlledCarrier (VSS) : ground or power negative terminal VEE: negative voltage power supply; Source (S)VPP of the field effect tube: Programming/erasing voltage.
  VCC: C=circuit indicates the meaning of the circuit, that is, the voltage of the access circuit;
  VDD: D=device indicates the meaning of the device, that is, the operating voltage inside the device;
  VSS: S=series indicates the meaning of common connection, usually refers to the circuit common ground terminal voltage.

2. Another explanation:

  Vcc and Vdd are the power ends of the device.
  Vcc is positive for bipolar devices, and Vdd is mostly positive for single-stage devices. The subscript can be understood as the collector C of the NPN transistor, and the drain D of the PMOSorNMOS FET. Also you can see Vee and Vss in the circuit diagram, meaning the same thing. Because the dominant chip structure is silicon NPN, Vcc is usually positive. If you use the PNP structure, Vcc is negative. When selecting the chip, be sure to see the electrical parameters.
  Vcc comes from the collector supply voltage,CollectorVoltage, generally used in bipolar transistors,PNP tube for negative supply voltage, sometimes also marked as -Vcc,NPN tube for positive voltage.
  Vdd is derived from drain supply voltage,DrainVoltage, used in MOS transistor circuits, and generally refers to the power supply. Since PMOS transistors are rarely used alone, Vdd is often connected to the source of the PMOS tube in CMOS circuits.
  The Vss source power supply voltage refers to negative power supply in CMOS circuits, and zero volts or ground in single power supply.
  Vee emitter voltage,EmitterVoltage, generally used in ECL circuit negative supply voltage.
  Vbb base supply voltage for common base circuits in bipolar transistors.

3. Instructions

  3.1, generally speaking, VCC= analog power supply,VDD= digital power supply,VSS= digital ground,VEE= negative power supply.
  3.2, some ics have both VDD pins and VCC pins, indicating that this device itself has a voltage conversion function.
  3.3, for digital circuits, VCC is the power supply voltage of the circuit,VDD is the working voltage of the chip (usually Vcc>Vdd), VSS is the ground point.
  3.4, in the field effect tube (or COMS device), VDD is the drain, VSS is the source, VDD and VSS refer to the component pin, and do not indicate the supply voltage.
  Detail: Some ics have both VCC and VDD, this device has a voltage conversion function. In the "field effect" i.e. COMS component, VDD is the drain pin of CMOS, VSS is the source pin of CMOS, this is the component pin symbol, it does not have the name "VCC", your question contains 3 symbols, VCC/VDD /VSS, VCC /VSS, VCC /VSS, VCC/VDD /VSS. This is obviously a circuit symbol in addition to the correct grounding design and installation, but also the correct grounding processing of various different signals.
  In the control system, there are roughly the following ground lines:
  (1) Digitally: also called logically, it is the zero potential of various switching quantities (digital quantities) signals.
  (2) Analog ground: is the zero potential of various analog signals.
  (3) Signal ground: usually the ground of the sensor.
  (4) AC ground: the ground wire of the AC power supply, which is usually the ground that generates noise.
  (5) DC ground: DC power supply ground.
  (6) Shielding ground: also called shell ground, to prevent electrostatic induction and magnetic field induction.
  The above ground processing is an important problem in system design, installation and commissioning.

  The following are some views on the grounding issue:

  (1) The control system should be grounded at one point. Under normal circumstances, the high-frequency circuit should be grounded at the nearest multi-point, and the low-frequency circuit should be grounded at one point. In low-frequency circuits, the inductance between wiring and components is not a big problem, but the interference effect of the grounding loop is very large, so a point is often used as the ground point; However, one-point grounding is not applicable to high frequencies, because at high frequencies, there is inductance on the ground wire, which increases the ground impedance, and inductive coupling between different lines is generated. Generally speaking, the frequency is below 1MHz, which can be grounded at one point; When the frequency is higher than 10MHz, multipoint grounding is used. It can be grounded at one point or multiple points between 1 and 10 MHZ.
    (2) The communication ground and the signal ground cannot be shared. Since there will be several mV or even several V voltages between two points of a power line, this is a very important interference for low-level signal circuits, so it must be isolated and prevented.
    (3) Comparison between floating and grounding. The whole machine floating is that each part of the system is floating with the earth, this method is simple, but the insulation resistance of the whole system and the earth can not be less than 50MΩ. This method has a certain anti-interference ability, but once the insulation drops, it will bring interference. Another method is to ground the casing and float the rest. This method has strong anti-interference ability, safety and reliability, but it is more complicated to implement.
    (4) Simulatively. The connection of simulated ground is very important. In order to improve the ability to resist common-mode interference, shielding floating technology can be used for analog signals. The grounding treatment of the specific analog signal should be strictly designed in accordance with the requirements of the operation manual.
    (5) Shielded area. In order to reduce the capacitive coupling noise in the signal, detect and control accurately, it is necessary to adopt shielding measures for the signal. According to the different purpose of shielding, the connection of shielding ground is also different. Electric field shielding to solve the problem of distributed capacitance, generally ground; Electromagnetic shielding mainly avoids interference from high-frequency electromagnetic fields such as radar and radio. Made of low resistance metal material with high conductivity, can be ground. Magnetic field shielding to prevent magnets, motors, transformers, coils and other magnetic induction, the shielding method is to use high-permeability magnetic materials to close the magnetic circuit, generally ground is good. When the signal circuit is one-point grounding, the shielding layer of the low-frequency cable should also be one-point grounding. If there is more than one shield site of the cable, noise current will be generated, forming a noise interference source. When a circuit has an ungrounded signal source connected to a grounded amplifier in the system, the input shield should be connected to the common end of the amplifier; In contrast, when a grounded signal source is connected to an ungrounded amplifier in the system, the input end of the amplifier should also be connected to the common end of the signal source. For the grounding of the electrical system, it should be classified according to the requirements and purposes of the grounding, and different types of grounding can not be simply and arbitrarily connected together, but it should be divided into several independent grounding subsystems, each subsystem has its common ground point or grounding trunk, and finally connected together to implement total grounding.
 
    Some people say: analog and digital, eventually have to receive a piece, then why also divide analog and digital? This is because although they are connected, the longer the distance, it is different. The voltage at different points of the same wire may be different, especially when the current is large. Because there is resistance in the wire, there is a voltage drop when the current flows through. In addition, the wire has a distributed inductance, and the influence of the distributed inductance will be shown under the AC signal. So we have to divide into digital and analog, because the high frequency noise of the digital signal is very large, if the analog and digital mixture, it will transmit the noise to the analog part, causing interference. If grounded separately, high-frequency noise can be isolated by filtering at the power supply. But if you mix the two, it's not easy to filter.

    We often see 0 ohm resistance in the circuit, for beginners, often very confused: since it is 0 Ohm resistance, that is the wire, why install it? Are there any resistors like this on the market? In fact, a resistance of 0 ohm is quite useful.
    It has the following functions:
    ① Used as a jumper. This is both beautiful and easy to install.
    In digital and analog hybrid circuits, the two are often required to be separated and connected at a single point. Instead of connecting the two places directly, we can connect them with a 0 ohm resistor. The advantage of this is that the ground line is divided into two networks, which will be much more convenient when processing large areas of copper. In such cases, inductors or magnetic beads are sometimes used to connect.
    ③ For fuses. Because the fusing current on the PCB is large, if there is a fault such as short circuit overcurrent, it is difficult to fuse, which may bring a greater accident. Because the 0 ohm resistance current bearing capacity is relatively weak (in fact, the 0 Ohm resistance also has a certain resistance, but it is very small), the 0 Ohm resistance is first fused when the current is over, so as to disconnect the circuit and prevent the occurrence of greater accidents. Sometimes some small resistors with a resistance value of a few tenths or a few ohm are used to make fuses. However, it is not recommended to use this way, but some manufacturers will use this in order to save costs.
    ④ Reserved position for debugging. You can decide whether to install or not, or other values, as needed. Sometimes it is also marked with *, indicating that it is determined by debugging.
    ⑤ Used as a configuration circuit. This function is similar to a jumper or dip switch, but it is fixed by welding, so that ordinary users can avoid modifying the configuration at will. By installing resistors at different locations, you can change the function of the circuit or set the address. 0 ohm resistance is not only sold, but also has different specifications, generally according to power points, such as 1/8 watt, 1/4 watt and so on. How to choose? This depends on the product data sheet. It has resistance values and power values.
    Whether it is in the analog circuit or in the digital circuit there are a variety of "ground", in order to facilitate everyone to understand and grasp, it is summarized for your reference.

    1. Signal "ground" :
    The signal "ground" is also called the reference "ground", which is the reference point of zero potential, and also the common segment of the circuit signal loop, and the graphic symbol "⊥".
    1) DC ground: DC circuit "ground", zero potential reference point.
    2) Alternating current: neutral line of alternating current. It should be distinguished from ground lines.
    3) Power ground: zero potential reference point of high-current network devices and power amplifier devices.
    4) Analog ground: zero potential reference points for amplifiers, sample holders, A/D converters and comparators.
    5) Digital: also called logical, is the zero potential reference point of the digital circuit.
    6) "hot ground" : the switching power supply does not need to use a transformer, the "ground" of its switching circuit is related to the mains power grid, the so-called "hot ground", it is charged, the graphic symbol is: "⊥".
    7) "cold ground" : because the high-frequency transformer of the switching power supply will isolate the input and output terminals; And because the feedback circuit is usually photoelectric coupling, it can transmit the feedback signal and isolate the "ground" of the two sides. So the output ground is called "cold ground", it is not charged. The graphical symbol is "⊥".
    2. Protect the "ground" :
    Protection "ground" is a connection mode set up to protect the safety of personnel. One end of the "ground" line is connected to the electrical appliance, and the other end is reliably connected to the earth.
    3. The "ground" in the audio:
    1) Shielded wire grounding: In order to prevent interference in the sound system, the metal housing is connected with the signal "ground", which is called shielded grounding.
    2) Audio special "ground" : In order to prevent interference, in addition to shielding the "ground", professional audio also needs to be connected with the audio special "ground". The grounding device should be specially buried, and should be connected with the isolation transformer and the corresponding grounding terminal of the shielded voltage regulator power supply as a special audio ground point in the audio control room.
    4. Treatment methods of different ground lines:
    1) Digital and analog should be separated: In high-demand circuits, digital and analog must be separated. Even for A/D, D/A converters on the same chip on the two "ground" is best to separate, only at a point in the system to connect the two "ground".
    2) Protect the "ground" : protect the "ground" is a connection mode set up to protect the safety of personnel. One end of the "ground" line is connected to the electrical appliance, and the other end is reliably connected to the earth.
    3) The "ground" in the audio:
    a) Shielded wire grounding: In order to prevent interference in the sound system, the metal housing is connected to the signal "ground" with a wire, which is called shielded grounding.
    b) Audio special "ground" : In order to prevent interference, in addition to shielding the "ground", professional audio needs to be connected with the audio special "ground". The grounding device should be specially buried, and should be connected with the isolation transformer and the corresponding grounding terminal of the shielded voltage regulator power supply as a special audio ground point in the audio control room.
    4) Floating and grounding: The system is floating, which means that the ground wire of each part of the system circuit is floating up and not connected to the earth. This connection method has certain anti-interference ability. However, the insulation resistance between the system and the ground cannot be less than 50MΩ, and once the insulation performance is reduced, it will bring interference. Usually, the system is floating and the housing is grounded, which can enhance the anti-interference ability and make it safe and reliable.
    5) One point grounding: In low-frequency circuits, there is not much impact between wiring and components. Generally, circuits with frequencies less than 1MHz are grounded at one point.
    6) Multi-point grounding: In high-frequency circuits, the influence of parasitic capacitance and inductance is greater. Generally, a circuit with a frequency greater than 10MHz uses multi-point grounding.