![]() ![]() Both approaches can reduce switching losses.Ĭompared with the bipolar transistor, it is generally believed that no current is required to make the MOS tube conductive, as long as the GS voltage is above a certain value. Shortening the switching time can reduce the loss at each conduction reducing the switching frequency can reduce the number of switches per unit of time. The product of voltage and current at the moment of conduction is very large, and the resulting loss is also very large. Usually, the switching loss is much larger than the conduction loss, and the higher the switching frequency, the larger the loss. the voltage at both ends of the MOS has a falling process, the flow of current has a rising process, in this time, the MOS tube loss is the product of voltage and current, called switching losses. MOS in the conduction and cut-off time, must not be completed in an instant. Now the low-power MOS tube on resistance is generally in the tens of milliohms or so, a few milliohms are also available. Selecting a MOS tube with a small on-state resistance will reduce the on-state losses. Whether it is NMOS or PMOS, there is an on-resistance after conduction, so the current will consume energy in this resistance, this part of the consumed energy is called conduction loss. However, although PMOS can be easily used as a high-end driver, but due to the large on-resistance, expensive, fewer replacement types, etc., the high-end driver, usually still uses NMOS. PMOS has the characteristic that Vgs will turn on when it is less than a certain value and is suitable for the case when the source is connected to VCC (high-end drive). NMOS characteristics, Vgs greater than a certain value will be on, suitable for use in the case of source ground (low-end drive), as long as the gate voltage of 4V or 10V can be. By the way, the body diode is only present in a single MOS tube and is usually not present inside the IC chip. This is called the body diode and is important in driving inductive loads (such as motors). As you can see on the MOS tube schematic, there is a parasitic diode between the drain and the source. We commonly use NMOS because of its low on-resistance and easy manufacturing. In practical projects, we use enhanced mos tubes, which are divided into two types: N-channel and P-channel. What are the differences between nmos and pmos? However, because PMOS circuits are simple and inexpensive, some medium-scale and small-scale digital control circuits still use PMOS circuit technology. PMOS operates at a much lower speed because of its large logic swing and long charging and discharging process, coupled with the small trans-conductance of the device, and after NMOS circuits (see N-channel metal-oxide-semiconductor integrated circuits), most of them have been replaced by NMOS circuits. The voltage magnitude and polarity of its power supply are not compatible with bipolar transistor-transistor logic circuits. In addition, the absolute value of the threshold voltage of P-channel MOS transistors is generally high and requires a higher operating voltage. PMOS is an n-type substrate, p-channel, MOS tube that relies on the flow of holes to carry current.Ĭhannel MOS transistors have low hole mobility, and thus the trans-conductance of PMOS transistors is smaller than that of N-channel MOS transistors when the geometry and operating voltage of MOS transistors are equal in absolute value. An integrated circuit made up of MOS tubes is called a MOS integrated circuit, a circuit made up of NMOS is an NMOS integrated circuit, a circuit made up of PMOS tubes is PMOS integrated circuit, and a complementary MOS circuit made up of both NMOS and PMOS tubes is CMOS circuit. MOS transistor has a P-type MOS tube and an N-type MOS tube. It means N-type metal-oxide-semiconductor, and the transistor with this structure we call NMOS transistor. NMOS is called N-Metal-Oxide-Semiconductor in English. If you want to know how to choose the correct MOS tube, please refer to the article titled How to choose the correct MOS tube. By reading this article, you can learn the difference between nmos and pmos and the application of both, so that you can apply them better. This article focuses on the difference between nmos and pmos. ![]()
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