There is essentially no difference between positive and negative voltages. According to Ohm's law: current X voltage = electric power. There is no requirement for the polarity of the voltage, as long as there is a potential difference there will be a current through the load. So both the positive voltage and the negative voltage do the same work.
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In the circuit known as negative voltage generally have the following cases:
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In a positive grounded DC circuit, all the charged points are negative. For example, circuits made of PNP transistors are \"the world of negative electricity\".
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However, the same circuit, changing the transistor to NPN type, requires a positive voltage supply. But there is no difference in function between the two circuits.
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② Circuit with positive and negative power supply
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This power supply mode is often used in digital circuits and power amplification circuits. Because the circuit amplifies the positive half-cycle and negative half-cycle signals, the transistors used for positive and negative half-cycle operation respectively must be powered by the corresponding positive and negative power sources. This ensures that there is no DC component on the load.
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If a single power supply is used, the voltage at the load is equivalent to 1\/2 of the power supply voltage, and then a direct capacitor has to be added to block the DC. The performance of such a circuit is greatly compromised.
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ac
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Negative electricity is an indispensable \"element\" of alternating current. For 50Hz AC, negative and positive electricity will appear 50 times each in a second, so that alternating magnetic fields can be generated, and with the help of transformers and motors and other equipment to complete the voltage rise and fall and mechanical operation. In this case, the negative and positive charges do exactly the same amount of work.
The gate voltage in an IGBT or MOSFET may be negative, for example, some use 15\/-5 V, and some use 15\/0 V. The use of negative voltage during shutdown can accelerate the discharge of the miller capacitor and prevent the misdirection caused by dv\/dt. Therefore, it is common to turn off miller clamping with negative voltage for high switching frequency or high Vds.
2, communication interface needs. For example, RS232 interfaces must use negative voltage. The value from -3V to -15V is 1, and the value from 3 to 15V is 0. This is the protocol when the communication interface was designed, so we have to abide by it. PS: Interface chips such as the MAX232 have charge pumps that can generate negative voltage on their own.
3. Provide power rail for (non-rail to rail) operation amplifier. Older opamps do not have rail-to-rail input\/output capabilities, such as the OP07, and the input voltage range is always 1V smaller than the supply voltage range, and the output is 2V smaller. So if VEE uses 0V, the input voltage must exceed 1V and the output voltage must not fall below 2V. This may not meet the design requirements of some circuits. In order to operate at input\/output conditions close to 0V, it is necessary to provide a negative voltage to the op amp, such as -5V, so that the operation can work properly near 0V. However, with the popularity of rail-to-rail amps, this situation is becoming less and less common.
4, Generally speaking, the protection circuit inside the chip is not fortified for negative voltage, so as long as there is a slightly larger current, the voltage does not need to be very high negative voltage added to the chip, you can successfully destroy the chip.
First of all, there is no record of a metal object producing negative voltage in a living room until a person dies. Some static electricity is possible. Keep a certain humidity in the room to prevent the accumulation of static electricity.
Highly insulated shoes, put on a down jacket, squeeze the bus, go home and touch metal objects may cause an electric shock, but it is not life-threatening. If there is an electric shock when you touch the faucet, it must be the static electricity carried by the individual, and the faucet has been well connected to the earth through the internal water.