You will see the 0 ohm resistor in the circuit, will you be confused?

DCpower generally refers to the source with the actual voltage, the others are the labels (in some simulation software, the default is to connect the label and the source) VDD: power supply voltage (unipolar device); power supply voltage (4000 series digital circuit); Pole voltage (field effect transistor) VCC: power supply voltage (bipolar device); power supply voltage (74 series digital circuit); voice control carrier (VoiceControlledCarrier) VSS: ground or power supply negative VEE: negative voltage supply; FET source ( S) VPP: Program/erase voltage.

DCpower generally refers to the source with the actual voltage, the others are the labels (in some simulation software, the default is to connect the label and the source) VDD: power supply voltage (unipolar device); power supply voltage (4000 series digital circuit); Pole voltage (field effect transistor) VCC: power supply voltage (bipolar device); power supply voltage (74 series digital circuit); voice control carrier (VoiceControlledCarrier) VSS: ground or power supply negative VEE: negative voltage supply; FET source ( S) VPP: Program/erase voltage.

VCC: C=circuit means the meaning of the circuit, that is, the voltage of the access circuit; VDD: D=device means the meaning of the device, that is, the working voltage inside the device; VSS: S=series means the meaning of the common connection, usually refers to the common ground of the circuit. Terminal voltage.

Vcc and Vdd are the power terminals 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 field effect transistor. You can also see Vee and Vss in the circuit diagram, which means the same. Since the mainstream chip structure is silicon NPN, Vcc is usually positive. If VNP is used, the PNP structure is negative. It is important to see the electrical parameters when selecting the chip.

Vcc is derived from the collector supply voltage, CollectorVoltage, which is generally used for bipolar transistors. The PNP tube is a negative supply voltage, sometimes labeled as -Vcc, and the NPN tube is a positive voltage.

Vdd is derived from the drain supply voltage, DrainVoltage, used in MOS transistor circuits, and is generally referred to as a positive supply. Since PMOS transistors are rarely used alone, Vdd is often connected to the source of the PMOS transistor in a CMOS circuit.

Vss source supply voltage, referred to as a negative supply in a CMOS circuit, or zero volt or ground on a single supply.

Vee emitter supply voltage, EmitterVoltage, is generally used for the negative supply voltage of the ECL circuit.

Vbb base supply voltage for common-base circuits of bipolar transistors.

1. Generally speaking, VCC=analog power supply, VDD=digital power supply, VSS=digital ground, VEE=negative power supply.

2. Some ICs have both VDD and VCC pins, indicating that the device itself has a voltage conversion function.

3. For digital circuits, VCC is the supply voltage of the circuit, VDD is the operating voltage of the chip (usually Vcc "Vdd"), and VSS is the ground point.

4. In a FET (or COMS device), VDD is the drain, VSS is the source, and VDD and VSS refer to the component pins, not the supply voltage.

Detailed explanation: Some ICs have both VCC and VDD. This device has a voltage conversion function. In the "field effect" or COMS component, VDD is the drain pin of CMOS, VSS is the source pin of CMOS, this is the component pin symbol, it has no "VCC" name, your question contains 3 symbols , VCC / VDD / VSS, this is obviously the circuit symbol in addition to the correct grounding design, installation, but also the correct grounding of various signals.

In the control system, there are roughly the following ground lines:

(1) Digital ground: Also called logical ground, it is the zero potential of various switching (digital) signals. (2) Analog ground: It 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 where noise is generated. (5) DC ground: the ground of the DC power supply. (6) Shielding ground: also called the chassis ground, designed to prevent static induction and magnetic field induction.

These ground wire treatments are an important issue in system design, installation, and commissioning.

Here are some thoughts on the grounding problem:

(1) The control system should be grounded at one point. Under normal circumstances, the high-frequency circuit should be grounded at multiple points, and the low-frequency circuit should be grounded at one point. In the low-frequency circuit, the inductance between the wiring and the component is not a big problem. However, the interference of the loop formed by the ground has a great influence. Therefore, the grounding point is often used as a grounding point; but one-point grounding is not suitable for the high frequency because the high frequency At the time, the ground line has an inductance, which increases the impedance of the ground line, and inductive coupling between the lines. Generally speaking, the frequency is below 1MHz, and one point can be grounded; when it is higher than 10MHz, multi-point grounding is used; one point can be grounded between 1~10MHz, and multiple points can be grounded.

(2) The exchange ground and the signal ground cannot be shared. Since there are several mV or even a few V voltages between two points of a power ground, this is a very important interference for low level signal circuits and must be isolated and prevented.

(3) Comparison of floating ground and grounding. The whole system is floating, that is, all parts of the system are floating with the earth. This method is simple, but the insulation resistance of the whole system and the earth cannot be less than 50MΩ. This method has a certain anti-interference ability, but it will cause interference once the insulation is lowered. Another method is to ground the case and leave the rest floating. This method is strong in anti-interference ability, safe and reliable, but it is complicated to implement.

(4) Analog ground. The connection of the analog ground is very important. In order to improve the anti-common mode interference capability, shielded floating technology can be used for analog signals. Grounding of specific analog signals should be designed in strict accordance with the requirements in the operation manual.

(5) Shielding ground. In the control system, in order to reduce the capacitive coupling noise in the signal, accurate detection and control, it is necessary to use shielding measures for the signal. Depending on the purpose of the shielding, the connection of the shielding ground is different.

Electric field shielding solves the problem of distributed capacitance, generally connected to the earth; electromagnetic field shielding mainly avoids high-frequency electromagnetic field radiation interference such as radar and radio. Made of high-conductivity of low-resistance metal materials, it can be grounded. The magnetic field shielding is used to prevent magnetic induction of magnets, motors, transformers, coils, etc. The shielding method is to use a high magnetic conductive material to close the magnetic circuit, generally it is better to connect the earth. When the signal circuit is grounded at one point, the shield of the low frequency cable should also be grounded at one point. If there is more than one shield location of the cable, a noise current will be generated, creating a source of noise interference. When a circuit has an ungrounded signal source connected to a grounded amplifier in the system, the shield at the input should be connected to the common terminal of the amplifier; conversely, when the grounded signal source is connected to an ungrounded amplifier in the system, the input to the amplifier The terminal should also be connected to the common end of the signal source.

For the grounding of electrical systems, it should be classified according to the requirements and purpose of grounding. It is not possible to simply and arbitrarily connect different types of grounding. Instead, it should be divided into several independent grounding subsystems, each with its common grounding point. Or ground the trunk, and finally connect together to implement the total grounding.

Some people say: The analog ground and the digital ground will eventually receive one piece. Why do you have to divide it into analog and digital grounds?

This is because although they are connected, the distance is long, it is different. On the same wire, the voltage at different points may be different, especially when the current is large. Because of the resistance of the wire, a voltage drop occurs when current flows. In addition, the wire also has a distributed inductance, and the effect of the distributed inductance is expressed under the AC signal. So we have to divide it into digital ground and analog ground, because the high frequency noise of the digital signal is very large. If the analog ground and the digital ground are mixed, the noise will be transmitted to the analog part, causing interference. If grounded separately, high frequency noise can be isolated by filtering at the power supply. But if the two grounds are mixed, it is not good to filter.

We often see 0 ohm resistors in the circuit. For newcomers, it is often confusing: since it is a 0 ohm resistor, it is a wire. Why should it be installed? Is there such a resistor sold in the market? In fact, the resistance of 0 ohms is quite useful.

There are probably the following features:

1 Use as a jumper. This is both beautiful and easy to install.

â‘¡ hybrid digital and analog circuits and the like, often require two separated, and a single point of connection. We can connect the two grounds with a 0 ohm resistor instead of directly connecting them together. The advantage of this is that the ground wire is divided into two networks, which is much more convenient when processing large areas of copper. With a hint, in such a case, it may be connected by an inductor or a magnetic bead.

3 Use as a fuse. Since the fuse current of the trace on the PCB is large, if a fault such as a short circuit or an overcurrent occurs, it is difficult to blow, which may cause a larger accident. Since the 0 ohm resistor current withstand capability is relatively weak (in fact, the 0 ohm resistor also has a certain resistance, it is only a small one), when the overcurrent is first, the 0 ohm resistor is blown, thereby disconnecting the circuit and preventing a larger accident. happened. Sometimes a small resistor with a resistance of a few tenths or a few ohms is used as a fuse. However, it is not recommended to use this, but some manufacturers will use this in order to save costs.

4 The location reserved for debugging. You can decide whether to install, or other values, as needed. Sometimes it will be marked with *, which is determined by the time of debugging.

5 Used as a configuration circuit. This function is similar to a jumper or a DIP switch, but is fixed by soldering, thus avoiding the ordinary user to modify the configuration at will. By installing resistors in different locations, you can change the function of the circuit or set the address. The 0 ohm resistor is not only sold, but also has different specifications. It is usually divided by power, such as 1/8 watt, 1/4 watt, and so on. How to choose? This requires a look at the product data sheet. It has resistance and power values.

Whether in the analog circuit or in the digital circuit, there are all kinds of "grounds". For the sake of understanding and mastering, we will summarize them for your reference.

1. Signal "ground":

The signal "ground", also known as the reference "ground", is the reference point of zero potential, and is also the common segment of the circuit signal loop, the graphic symbol "⊥".

1) DC ground: DC circuit "ground", zero potential reference point.

2) Exchange place: the neutral line of AC power. Should be distinguished from the ground.

3) Power ground: zero potential reference point for high current network devices and power amplifier devices.

4) Analog ground: Zero potential reference point for amplifier, sample and hold, A/D converter and comparator.

5) Digital ground: also called logic ground, 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 the switching circuit is related to the mains power grid. It is called "hot ground". It is charged and the graphic symbol is: "⊥".

7) "Cold ground": Because the high-frequency transformer of the switching power supply isolates the input and output terminals; and because its feedback circuit is commonly used for photoelectric coupling, it can transmit feedback signals and isolate the "ground" of both sides; For "cold land", it is not charged. The graphic symbol is “⊥”.

2. Protect "land":

Protection "ground" is a type of wiring that is set to protect personnel. One end of the protection "ground" line is connected to the electrical appliance, and the other end is reliably connected to the earth.

3. "Ground" in the sound:

1) Shielded wire grounding: In order to prevent interference, the sound system of the metal case is connected with the signal “ground”. This is called shield grounding.

2) Audio dedicated "ground": In order to prevent interference, professional audio must be connected to the audio dedicated "ground" in addition to shielding the "ground". This grounding device should be buried specifically and should be connected to the corresponding grounding of the isolation transformer and the shielded regulated power supply as a dedicated audio grounding point in the sound control room.

4. Different ground wire treatment methods:

1) Digital ground and analog ground should be separated: in high-demand circuits, digital ground must be separated from analog ground. Even for the A/D, D/A converter, the two "grounds" on the same chip should be separated, and only the two "grounds" are connected at one point in the system.

2) Protection of "ground": Protection of "ground" is a wiring method set to protect personnel safety. One end of the protection "ground" line is connected to the electrical appliance, and the other end is reliably connected to the earth.

3) "Ground" in the sound:

a) Shielded wire grounding: In order to prevent interference, the sound system of the metal case is connected with the signal “ground”. This is called shield grounding.

b) Audio-specific “ground”: In order to prevent interference, professional audio must be connected to “dedicated” “audio” in addition to shielding “ground”. This grounding device should be buried specifically and should be connected to the corresponding grounding of the isolation transformer and the shielded regulated power supply as a dedicated audio grounding point in the sound control room.

4) Floating and grounding: The system floats, which floats the ground of each part of the system circuit and is not connected to the earth. This connection has a certain anti-interference ability. However, the insulation resistance between the system and the ground should not be less than 50 MΩ. Once the insulation performance is degraded, it will cause interference. The system is usually floating and the chassis is grounded to enhance the anti-interference ability, which is safe and reliable.

5) One-point grounding: In low-frequency circuits, there is no significant influence between wiring and components. Generally, circuits with a frequency less than 1MHz are grounded at one point.

6) Multi-point grounding: In high-frequency circuits, the influence of parasitic capacitance and inductance is large. Generally, circuits with a frequency greater than 10 MHz are grounded at multiple points.